Auto merge of rust-lang#128651 - folkertdev:naked-asm-macro-v2, r=Amanieu

add `naked_asm!` macro for use in `#[naked]` functions

tracking issue: rust-lang#90957

Adds the `core::arch::naked_asm` macro, to be used in `#[naked]` functions, but providing better error messages and a place to explain the restrictions on assembly in naked functions.

This PR does not yet require that the `naked_asm!` macro is used inside of `#[naked]` functions:

- the `asm!` macro can still be used in `#[naked]` functions currently, with the same restrictions and error messages as before.
- the `naked_asm!` macro can be used outside of `#[naked]` functions. It has not yet been decided whether that should be allowed long-term.

In this PR, the parsing code of `naked_asm!` now enforces the restrictions on assembly in naked functions, with the exception of checking that the `noreturn` option is specified. It also has not currently been decided if `noreturn` should be implicit or not.

This PR looks large because it touches a bunch of tests. The code changes are mostly straightforward I think: we now have 3 flavors of assembly macro, and that information must be propagated through the parsing code and error messages.

cc `@Lokathor`

r? `@Amanieu`

Author: bors