[lld] [lld][LoongArch] Support the R_LARCH_{ADD,SUB}_ULEB128 relocation types (PR #81133)

[Lu Weining via llvm-commits]

SixWeining wrote:

> Thanks for reviewing the change, but please do not land. For LoongArch linker changes and changes to the generic assembler code, there have been many instances in the past where more adjustments were needed and suggested by me. I appreciate that you wait on my input.

Thanks. No problem. I'll not land it until all review comments are addressed.

https://github.com/llvm/llvm-project/pull/81133