[clang] [lld] [llvm] [lld][WebAssembly][Clang][MC] WASIP3 and component model threading support (PR #175800)

[Sam Clegg via cfe-commits]

sbc100 wrote:

> @sbc100 I've added [Clang] and [MC] to the title prefix. Since it's a fairly fundamental change to how code for WASIP3 is compiled I included all the end-to-end changes.
> 
> Landing it piecemeal seems more challenging due to how the changes in the upper layers also need supporting changes in the linker, but I'm happy to split this into multiple PRs if it will aid review.

Fair enough.   I think we can just use `[WebAssembly]` for the prefix when its cross cutting like this.

https://github.com/llvm/llvm-project/pull/175800