Consider renaming files named `mod.rs/x86_64.rs/aarch64.rs` to more unique filenames

[ludfjig]

Having multiple files with same name makes it annoying to search and find specific files.

For the x86_64.rs/aarch64.rs files (example src/hyperlight_host/src/hypervisor/hyperlight_vm/x86_64.rs) we could put them in a folder with that name instead (as we already do in certain places for example src/hyperlight_host/src/hypervisor/regs/x86_64/special_regs.rs).

For mod.rs file we can consider moving to the newer rust module convention which uses less mod.rs files.

I'm not saying all existing files must be renamed and are all bad, but I personally would like a bit more uniqueness