zstd: Improve Best compression

[klauspost]

Compare expected literal encoding to predefined table code side and increase table sizes.

Before/after:

enwik8	zskp	4	100000000	31421593	4230	22.54
enwik8	zskp	4	100000000	29988041	9278	10.28
 => 4.6% better

silesia.tar	zskp	4	211947520	60995370	8825	22.90
silesia.tar	zskp	4	211947520	60104364	18082	11.18
 => 1.5% better

gob-stream	zskp	4	1911399616	167273881	30734	59.31
gob-stream	zskp	4	1911399616	165609838	50369	36.19
 => 1.0% better

github-ranks-backup.bin	zskp	4	1862623243	393605175	66308	26.79
github-ranks-backup.bin	zskp	4	1862623243	383959113	127082	13.98
 => 2.5% better

nyc-taxi-data-10M.csv	zskp	4	3325605752	490907191	80377	39.46
nyc-taxi-data-10M.csv	zskp	4	3325605752	476268884	135958	23.33
 => 3.0% better