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

[via llvm-commits]

llvmbot wrote:

<!--IGNORE-->
Failed to cherry-pick: [9cbbb74](https://github.com/llvm/llvm-project/commit/9cbbb74d370c09e13b8412f21dccb7d2c4afc6a4)

https://github.com/llvm/llvm-project/actions/runs/14705758050

Please manually backport the fix and push it to your github fork.  Once this is done, please create a [pull request](https://github.com/llvm/llvm-project/compare)

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