[clang] [llvm] [dwarf] make dwarf fission compatible with RISCV relaxations (PR #164128)

[via llvm-commits]

dlav-sc wrote:

@dwblaikie, @lenary I've created 3 stacked PRs: refactoring (https://github.com/llvm/llvm-project/pull/164811), rnglists changes (https://github.com/llvm/llvm-project/pull/164812), low/high pc changes (https://github.com/llvm/llvm-project/pull/164813) 

https://github.com/llvm/llvm-project/pull/164128