branch-3.1: [fix](decimal256) fix casting decimal256 to float #54140

[jacktengg]

picked from #54140

[Thearas]

Thank you for your contribution to Apache Doris.
Don't know what should be done next? See How to process your PR.

Please clearly describe your PR:

1. What problem was fixed (it's best to include specific error reporting information). How it was fixed.
2. Which behaviors were modified. What was the previous behavior, what is it now, why was it modified, and what possible impacts might there be.
3. What features were added. Why was this function added?
4. Which code was refactored and why was this part of the code refactored?
5. Which functions were optimized and what is the difference before and after the optimization?

[jacktengg]

run buildall

[hello-stephen]

BE UT Coverage Report

Increment line coverage 0.00% (0/7) 🎉

Increment coverage report
Complete coverage report

Category	Coverage
Function Coverage	45.42% (12637/27822)
Line Coverage	36.27% (112669/310628)
Region Coverage	35.31% (58225/164896)
Branch Coverage	32.51% (31665/97414)

[doris-robot]

TPC-H: Total hot run time: 32595 ms

machine: 'aliyun_ecs.c7a.8xlarge_32C64G'
scripts: https://github.com/apache/doris/tree/master/tools/tpch-tools
Tpch sf100 test result on commit ba629ba55a051cba317eca92e06e1d452f2e359d, data reload: false

------ Round 1 ----------------------------------
q1	17679	5499	5462	5462
q2	2057	314	166	166
q3	10604	1235	753	753
q4	10237	878	456	456
q5	8198	2409	2091	2091
q6	178	166	133	133
q7	914	752	620	620
q8	9335	1443	1177	1177
q9	5283	4978	4939	4939
q10	6775	2283	1827	1827
q11	478	285	255	255
q12	330	348	219	219
q13	17788	3615	3003	3003
q14	228	219	221	219
q15	533	469	464	464
q16	425	440	389	389
q17	603	871	370	370
q18	6867	6465	6387	6387
q19	2017	963	549	549
q20	315	341	199	199
q21	2802	2154	1941	1941
q22	1055	1027	976	976
Total cold run time: 104701 ms
Total hot run time: 32595 ms

----- Round 2, with runtime_filter_mode=off -----
q1	5595	5448	5511	5448
q2	228	325	239	239
q3	2181	2606	2318	2318
q4	1319	1815	1308	1308
q5	4447	4898	4978	4898
q6	165	162	129	129
q7	2066	1927	1856	1856
q8	2615	2825	2661	2661
q9	7281	7280	7189	7189
q10	2997	3326	2782	2782
q11	562	510	480	480
q12	646	718	595	595
q13	3428	3795	3184	3184
q14	296	291	259	259
q15	529	474	468	468
q16	439	492	460	460
q17	1195	1720	1258	1258
q18	7626	7427	7230	7230
q19	798	1163	1027	1027
q20	2011	2047	1924	1924
q21	5221	4915	4672	4672
q22	1099	1048	997	997
Total cold run time: 52744 ms
Total hot run time: 51382 ms

[doris-robot]

TPC-DS: Total hot run time: 197583 ms

machine: 'aliyun_ecs.c7a.8xlarge_32C64G'
scripts: https://github.com/apache/doris/tree/master/tools/tpcds-tools
TPC-DS sf100 test result on commit ba629ba55a051cba317eca92e06e1d452f2e359d, data reload: false

query1	1331	914	889	889
query2	6246	2029	1986	1986
query3	11002	4503	4442	4442
query4	32963	24197	23838	23838
query5	4529	623	460	460
query6	297	180	174	174
query7	4019	497	318	318
query8	285	237	228	228
query9	9390	2604	2602	2602
query10	491	336	255	255
query11	18064	15435	15357	15357
query12	168	110	104	104
query13	1555	544	421	421
query14	8786	6860	6767	6767
query15	206	207	186	186
query16	7820	668	416	416
query17	1585	755	612	612
query18	2031	416	326	326
query19	207	189	172	172
query20	125	118	118	118
query21	207	126	113	113
query22	4609	4607	4429	4429
query23	34973	34162	34051	34051
query24	7811	2783	2746	2746
query25	513	489	438	438
query26	989	289	181	181
query27	2774	478	361	361
query28	5364	2251	2206	2206
query29	676	607	482	482
query30	239	201	163	163
query31	984	928	858	858
query32	70	60	56	56
query33	527	366	309	309
query34	753	856	534	534
query35	766	796	748	748
query36	1013	1052	964	964
query37	104	94	71	71
query38	4011	3986	4004	3986
query39	1604	1527	1474	1474
query40	206	121	111	111
query41	51	53	53	53
query42	136	116	108	108
query43	517	531	488	488
query44	1406	843	851	843
query45	189	178	173	173
query46	886	1061	677	677
query47	1952	2009	1906	1906
query48	401	427	355	355
query49	744	493	442	442
query50	706	690	416	416
query51	7555	7342	7284	7284
query52	100	101	91	91
query53	243	259	189	189
query54	544	568	473	473
query55	81	82	84	82
query56	276	266	260	260
query57	1300	1278	1232	1232
query58	239	226	225	225
query59	3174	3284	3060	3060
query60	295	294	276	276
query61	115	114	112	112
query62	804	768	707	707
query63	243	207	201	201
query64	3936	989	696	696
query65	3392	3273	3303	3273
query66	889	396	309	309
query67	15946	15686	15611	15611
query68	6445	849	538	538
query69	501	302	276	276
query70	1166	1089	1103	1089
query71	389	305	262	262
query72	6027	3732	3872	3732
query73	655	753	356	356
query74	10399	9188	9038	9038
query75	3182	3115	2719	2719
query76	3125	1168	767	767
query77	495	360	294	294
query78	10303	10283	9566	9566
query79	3391	919	595	595
query80	768	521	434	434
query81	512	258	223	223
query82	577	122	87	87
query83	165	156	143	143
query84	254	96	84	84
query85	791	373	306	306
query86	392	318	307	307
query87	4266	4324	4193	4193
query88	5085	2419	2372	2372
query89	403	330	310	310
query90	1737	191	194	191
query91	138	139	109	109
query92	71	57	52	52
query93	2485	903	550	550
query94	690	414	298	298
query95	352	277	276	276
query96	492	617	284	284
query97	3194	3272	3146	3146
query98	223	208	200	200
query99	1482	1412	1292	1292
Total cold run time: 295568 ms
Total hot run time: 197583 ms

[doris-robot]

ClickBench: Total hot run time: 29.09 s

machine: 'aliyun_ecs.c7a.8xlarge_32C64G'
scripts: https://github.com/apache/doris/tree/master/tools/clickbench-tools
ClickBench test result on commit ba629ba55a051cba317eca92e06e1d452f2e359d, data reload: false

query1	0.04	0.03	0.02
query2	0.07	0.03	0.03
query3	0.24	0.06	0.06
query4	1.63	0.11	0.11
query5	0.53	0.52	0.52
query6	1.12	0.73	0.73
query7	0.02	0.02	0.02
query8	0.04	0.02	0.03
query9	0.58	0.50	0.51
query10	0.55	0.56	0.58
query11	0.14	0.11	0.11
query12	0.14	0.10	0.11
query13	0.61	0.60	0.60
query14	0.76	0.79	0.79
query15	0.83	0.83	0.83
query16	0.38	0.39	0.39
query17	1.06	1.00	1.02
query18	0.23	0.23	0.22
query19	1.86	1.83	1.82
query20	0.01	0.01	0.02
query21	15.40	0.95	0.58
query22	0.75	0.76	0.69
query23	15.10	1.41	0.56
query24	2.94	0.90	0.97
query25	0.28	0.13	0.14
query26	0.32	0.14	0.13
query27	0.05	0.06	0.05
query28	13.58	1.05	0.43
query29	12.57	4.02	3.38
query30	0.26	0.10	0.08
query31	2.82	0.61	0.38
query32	3.22	0.54	0.46
query33	3.00	2.97	3.00
query34	16.83	5.25	4.56
query35	4.60	4.59	4.56
query36	0.64	0.49	0.48
query37	0.09	0.06	0.06
query38	0.05	0.03	0.03
query39	0.03	0.03	0.02
query40	0.15	0.13	0.13
query41	0.07	0.03	0.03
query42	0.03	0.03	0.02
query43	0.03	0.02	0.02
Total cold run time: 103.65 s
Total hot run time: 29.09 s

[hello-stephen]

BE Regression && UT Coverage Report

Increment line coverage 100.00% (7/7) 🎉

Increment coverage report
Complete coverage report

Category	Coverage
Function Coverage	76.20% (20947/27489)
Line Coverage	69.58% (215999/310420)
Region Coverage	67.61% (129292/191233)
Branch Coverage	61.14% (67216/109938)

[hello-stephen]

BE Regression && UT Coverage Report

Increment line coverage 100.00% (7/7) 🎉

Increment coverage report
Complete coverage report

Category	Coverage
Function Coverage	76.20% (20947/27489)
Line Coverage	69.58% (215999/310420)
Region Coverage	67.61% (129292/191233)
Branch Coverage	61.14% (67216/109938)