[ARM,MC] Support FDPIC relocations (#82187)

Linux kernel fs/binfmt_elf_fdpic.c supports FDPIC for MMU-less systems.
GCC/binutils/qemu support FDPIC ABI for ARM
(https://github.com/mickael-guene/fdpic_doc).
_ARM FDPIC Toolchain and ABI_ provides a summary.

This patch implements FDPIC relocations to the integrated assembler.
There are 6 static relocations and 2 dynamic relocations, with
R_ARM_FUNCDESC as both static and dynamic.

gas requires `--fdpic` to assemble data relocations like `.word
f(FUNCDESC)`.
This patch adds `MCTargetOptions::FDPIC` and reports an error if FDPIC
is not set.