[lld] [LLD][COFF] Separate EC and native exports for ARM64X (PR #123652)

[Martin Storsjö via llvm-commits]

https://github.com/mstorsjo approved this pull request.

LGTM, assuming the large amount of moved code is unmodified (except for references to the fields that are moved around).

It's somewhat sad to see that we need to move this amount of code from Driver* into SymbolTable, but I guess it follows from the fact that this needs to operate on both namespaces separately.

https://github.com/llvm/llvm-project/pull/123652