[Hexagon] Add CFI-ICall sanitizer support (#191754)
Enable -fsanitize=cfi-icall for Hexagon targets:
- Add Hexagon to the CFI-ICall allow-list in the Clang driver.
- Add Hexagon jump table support in LowerTypeTests: 4-byte entries using
the `jump` instruction, and route Hexagon through the native function
bit-set builder.
