[lld] [LLD][COFF] Store and validate load config in SymbolTable (PR #120324)

[Jacek Caban via llvm-commits]

cjacek wrote:

We already look up the load configuration in two places in the writer, and ARM64X will require more of it, so storing it in the symbol table is more convenient. This change also replaces `Fatal` with `Err` for invalid load configurations and adds tests for these cases.

https://github.com/llvm/llvm-project/pull/120324