[lld] [LLD][ELF] Support 'i' and 'l' memory region attributes (PR #110937)

[Fangrui Song via llvm-commits]

MaskRay wrote:

I know one RISC-V firmware that uses `i` and it is semi-erroneous. Perhaps we were looking at the same instance.

`i` in BFD corresponds to `SEC_LOAD` but IMO the flag would only lead to confusion and erroneous behaviors. If `.bss` and the preceding section are not in the same memory region, very likely the BSS size optimization will not be effective. Therefore, I don't think we should add `i`.

https://github.com/llvm/llvm-project/pull/110937