dolt diff does not handle decimal precision change

[liuliu-dev]

repro:
change the column type from decimal(10,2) to decimal(10,4):

test/main> alter table decimalchange modify column col1 decimal(10,4);
liulius-MacBook-Pro:test liuliu$ dolt commit -m "change decimal"
commit 5c8avgpcfvap0mresh4m69sf5233r20k (HEAD -> main) 
Author: liuliu <liu@dolthub.com>
Date:  Tue Nov 12 12:34:03 -0800 2024

        change decimal

dolt diff with previous commit:

liulius-MacBook-Pro:test liuliu$ dolt diff fslnepcn3k61h85e4ab9qdjnrp900a4c 5c8avgpcfvap0mresh4m69sf5233r20k

output:

diff --dolt a/decimalchange b/decimalchange
--- a/decimalchange
+++ b/decimalchange
 CREATE TABLE `decimalchange` (
   `pk` int NOT NULL,
-  `col1` decimal(10,2) NOT NULL,
+  `col1` decimal(10,4),
   PRIMARY KEY (`pk`)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_bin;
+---+----+-------+
|   | pk | col1  |
+---+----+-------+
| < | 1  | 90.94 |
| > | 1  | 90.94 |
+---+----+-------+

related issue on dolthub:
dolthub/dolthub-issues#551

[jycor]

leftovers from this issue: #8133