Avoid emitting duplicate constant values in SPIR-V.

Previously, we had constant-value deduplication, based on the SkSL type
of the constant. However, we were still generating redundant constants,
because we would emit a separate constant for Float(n) and Half(n), or
Int(n) and Short(n), even though we generate the exact same instruction
for these constants. We now deduplicate based on the type's number-kind,
separating constant literals into three categories: floats, signed ints,
and unsigned ints. This better matches our type-handling in
getActualType.

Change-Id: I5777d4b3d567839b7aa72dc8de76908c18fc387e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/350031
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
16 files changed