[llvm] [LoongArch] Support R_LARCH_{ADD, SUB}_ULEB128 for .uleb128 and force relocs when sym is not in section (PR #76433)

[WÁNG Xuěruì via llvm-commits]

xen0n wrote:

Hmm, I didn't see the reason for the zero-padding behavior as requested by @MaskRay in the commit https://github.com/llvm/llvm-project/pull/76433/commits/5f771fee088f5029b278719f1a87b833a4492a14?

https://github.com/llvm/llvm-project/pull/76433