[DirectX] Legalize lifetime intrinsics for DXIL (#148003)
Fixes #147395
This PR legalizes lifetime intrinsics for DXIL by
- Adding a bitcast for the lifetime intrinsics' pointer operand in
dxil-prepare to ensure it gets cast to an `i8*` when written to DXIL
- Removing the memory attribute from lifetime intrinsics in dxil-prepare
to match DXIL
- Making the DXIL bitcode writer write the base/demangled name of
lifetime intrinsics to the symbol table
- Making lifetime intrinsics an exception to Int64Ops shader flag
analysis (otherwise we get `error: Flags must match usage.` from the
validator)
