Investigate CREL: compact relocation format for ELF

The CREL format for ELF relocations aims to reduce relocation section size via a more compact encoding:

https://maskray.me/blog/2024-03-09-a-compact-relocation-format-for-elf

Support is still evolving in LLVM (with ongoing patches, though x86-64 has been available for a while, e.g. since lld 16), but it may be worth exploring whether an experimental `ilc --experimental-elf-crel` or similar switch makes sense if it yields meaningful size savings for NativeAOT outputs.

One open question is how CREL interacts with the rest of the toolchain: does it require all input objects to be assembled with CREL support, or could emitting CREL from the object writer alone already provide benefits (i.e. mixing CREL and RELA inputs)?