[LoongArch] Add relaxDwarfLineAddr and relaxDwarfCFA to handle the mutable...

[LoongArch] Add relaxDwarfLineAddr and relaxDwarfCFA to handle the mutable label diff in dwarfinfo (#77728)

When linker-relaxation is enabled, part of the label diff in dwarfinfo
cannot be computed before static link. Refer to RISCV, we add the
relaxDwarfLineAddr and relaxDwarfCFA to add relocations for these label
diffs. Calculate whether the label diff is mutable. For immutable label
diff, return false and do the other works by its parent function.