[lld] Make hashtable entry size configurable (PR #113431)

[Dominik Steenken via llvm-commits]

dominik-steenken wrote:

@uweigand i have resolved the conflict, which was caused by the constructor parameters in `SyntheticSection` being changed on `main`. The PR is now ready to be merged again.

https://github.com/llvm/llvm-project/pull/113431