[lld] [LLD][COFF] Add S_THUNK32 PDB records for all ARM64EC import thunks (PR #115310)

[Jacek Caban via llvm-commits]

cjacek wrote:

Depends on #115309.

MSVC appears to use the demangled name for the auxiliary thunk. I followed this approach, which is why I pass `thunkSym` as the symbol for the auxiliary thunk chunk.

https://github.com/llvm/llvm-project/pull/115310