Change the "fixed encoding" table used for encoding intrinsic
type signature to use 16-bit encoding as opposed to 32-bit.
This results in both space and time improvements. For space,
the total static storage size (in bytes) of this info reduces by 50%:
- Current = 14193*4 (Fixed table) + 16058 + 3 (Long Table) = 72833
- New size = 14193*2 (Fixed table) + 19879 + 3 (Long Table) = 48268.
- Reduction = 50.9%
For time, with the added benchmark, we see a 7.3% speedup in
`GetIntrinsicInfoTableEntries` benchmark. Actual output of the
benchmark in included in the GitHub MR.
dcf0160bd6