[clang][bytecode] Slightly optimize integral casts of literals (#138879)

We often see initializers like

unsigned a = 10;

which take an integer literal and immediately cast it to another type.
Recognize this pattern and omit the cast, simply emitting the value as a
different type directly.

This reduces the instruction count by up to 0.13%:
http://llvm-compile-time-tracker.com/compare.php?from=303436c6d16518b35288d63a859506ffcc1681e4&to=648f5202f906d1606390b2d1081e4502dc74acc2&stat=instructions:u

0 files changed, 0 insertions, 0 deletions