[lld] [wasm-ld] Refactor WasmSym from static globals to per-link context (PR #134970)

[Fangrui Song via llvm-commits]

MaskRay wrote:

(I will have limited internet access between April 20th and May 4th, and my response time may be delayed..)

This is indeed similar to the ELF port and I hope we can move forward with this, but this needs @sbc100's approval.

https://github.com/llvm/llvm-project/pull/134970