Refactor emulated vector type handling for LLVM
Refactor emulated vector type handling for LLVM

- Add clarifying comments.
- Add self-explanatory helper functions.
- Fix typeSize to handle all Reactor types.
- Use uintptr_t base type for emulated type enum.
  Prevents 0x########00000000 from being interpreted as emulated type.

Bug b/126028338

Change-Id: Ib38cf9b59f58c0f6046f9c84a6152849791bb4ed
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/26648
Tested-by: Nicolas Capens <51edc787c30f24c4904e8ffbb5523c3a9f7a451d@google.com>
Reviewed-by: Ben Clayton <1f693eb7158dc33015048c09d6712f74dabddf79@google.com>

google/swiftshader,bkaradzic/SwiftShader,bkaradzic/SwiftShader,bkaradzic/SwiftShader,google/swiftshader,bkaradzic/SwiftShader,bkaradzic/SwiftShader,google/swiftshader