[ELF] Support R_RISCV_SET_ULEB128/R_RISCV_SUB_ULEB128 in non-SHF_ALLOC sections (#72610)

For a label difference like `.uleb128 A-B`, MC generates a pair of
R_RISCV_SET_ULEB128/R_RISCV_SUB_ULEB128 if A-B cannot be folded as a
constant. GNU assembler generates a pair of relocations in more cases
(when A or B is in a code section with linker relaxation).

`.uleb128 A-B` is primarily used by DWARF v5
.debug_loclists/.debug_rnglists (DW_LLE_offset_pair/DW_RLE_offset_pair
entry kinds) implemented in Clang and GCC.

`.uleb128 A-B` can be used in SHF_ALLOC sections as well (e.g.
`.gcc_except_table`). This patch does not handle SHF_ALLOC.

`-z dead-reloc-in-nonalloc=` can be used to change the relocated value,
if the R_RISCV_SET_ULEB128 symbol is in a discarded section. We don't
check the R_RISCV_SUB_ULEB128 symbol since for the expected cases A and
B should be defined in the same input section.