Support `preserve_none` calling convention on AArch64 targets

[antangelo]

#76868 adds support for a new preserve_none calling convention for X86_64 where all general registers are caller saved, and can be used to pass arguments. The corresponding RFC is here: https://discourse.llvm.org/t/rfc-exposing-ghccc-calling-convention-as-preserve-none-to-clang/74233

This issue is to track AArch64 support for the feature.

[llvmbot]

@llvm/issue-subscribers-backend-aarch64

Author: None (antangelo)

#76868 adds support for a new `preserve_none` calling convention for X86_64 where all general registers are caller saved, and can be used to pass arguments. The corresponding RFC is here: https://discourse.llvm.org/t/rfc-exposing-ghccc-calling-convention-as-preserve-none-to-clang/74233

This issue is to track AArch64 support for the feature.

[microcai]

any plans for Loongarch64 support?