Rename these relocation specifier constants, aligning with the naming
convention used by other targets (`S_` instead of `VK_`).
* ELF/COFF: AArch64MCExpr::VK_ => AArch64::S_ (VK_ABS/VK_PAGE_ABS are
also used by Mach-O as a hack)
* Mach-O: AArch64MCExpr::M_ => AArch64::S_MACHO_
* shared: AArch64MCExpr::None => AArch64::S_None
Apologies for the churn following the recent rename in #132595. This
change ensures consistency after introducing MCSpecifierExpr to replace
MCTargetSpecifier subclasses.
Pull Request: https://github.com/llvm/llvm-project/pull/144633