[CUDA][HIP] Fix mangling number for local struct

[CUDA][HIP] Fix mangling number for local struct

MSVC and Itanium mangling use different mangling numbers
for function-scope structs, which causes inconsistent
mangled kernel names in device and host compilations.

This patch uses Itanium mangling number for structs
in for mangling device side names in CUDA/HIP host
compilation on Windows to fix this issue.

A state is added to ASTContext to indicate whether the
current name mangling is for device side names in host
compilation. Device and host mangling number
are encoded/decoded as upper and lower half of 32 bit
unsigned integer to fit into the original mangling number
field for AST. Diagnostic will be emitted if a manglining
number exceeds limit.

Reviewed by: Artem Belevich, Reid Kleckner

Differential Revision: https://reviews.llvm.org/D122734

Fixes: SWDEV-328515