[ELF] Support NOCROSSREFS and NOCROSSERFS_TO
Implement the two commands described by
https://sourceware.org/binutils/docs/ld/Miscellaneous-Commands.html
After `outputSections` is available, check each output section described
by at least one `NOCROSSREFS`/`NOCROSSERFS_TO` command. For each checked
output section, scan relocations from its input sections.
This step is slow, therefore utilize `parallelForEach(isd->sections, ...)`.
To support non SHF_ALLOC sections, `InputSectionBase::relocations`
(empty) cannot be used. In addition, we may explore eliminating this
member to speed up relocation scanning.
Some parse code is adapted from #95714.
Close #41825
Pull Request: https://github.com/llvm/llvm-project/pull/98773
