[lld] wasm-ld: Implement function pointer alignment (PR #105532)

[Ethan O'Brien via llvm-commits]

ethanaobrien wrote:

Er-wait, I'm now getting the `null function or function signature mismatch` when building with the first function at a different start index. This needs to be changed elsewhere too?
![{670CD65F-ABB9-4F8A-BA46-CF0BFF94ADCD}](https://github.com/user-attachments/assets/2ed325f1-fa7d-4f8a-9b1d-99b114313646)


https://github.com/llvm/llvm-project/pull/105532