Permit asm_const and asm_sym to reference generic params

[nbdd0121]

Related #96557

These constructs will be allowed:

fn foofoo<const N: usize>() {}

unsafe fn foo<const N: usize>() {
    asm!("/* {0} */", const N);
    asm!("/* {0} */", const N + 1);
    asm!("/* {0} */", sym foofoo::<N>);
}

fn barbar<T>() {}

unsafe fn bar<T>() {
    asm!("/* {0} */", const std::mem::size_of::<T>());
    asm!("/* {0} */", const std::mem::size_of::<(T, T)>());
    asm!("/* {0} */", sym barbar::<T>);
    asm!("/* {0} */", sym barbar::<(T, T)>);
}

@Amanieu, I didn't switch inline asms to use DefKind::InlineAsm, as I see little value doing that; given that no type inference is needed, it will only make typecking slower and more complex but will have no real gains. I did switch them to follow the same code path as inline asm during symbol resolution, though.
The error: unconstrained generic constant you mentioned in #76001 is due to the fact that to_const will actually add a wfness obligation to the constant, which we don't need for asm_const, so I have that removed.

@rustbot label: +A-inline-assembly +F-asm

[rust-highfive]

r? @nagisa

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[Amanieu]

LGTM!

[nagisa]

We are missing a feature gate test for these constructs with generics I think.

[nagisa]

r=me once asm-const and asm-sym feature gate tests are augmented.

[Amanieu]

sym and const operands are still unstable, is it necessary to add a separate feature gate for their use with generics?

[nagisa]

I don't think its necessary to add an entirely separate test, but I think augmenting the existing feature-gate-asm_sym and feature-gate-asm_const with just one additional line each is probably worthwhile, if only to serve as a reminder when we look back at stabilizing these features.

[nagisa]

@bors r+

[bors]

📌 Commit 441d98f has been approved by nagisa

[bors]

⌛ Testing commit 441d98f with merge 10d9ecd...

[bors]

☀️ Test successful - checks-actions
Approved by: nagisa
Pushing 10d9ecd to master...

[rust-timer]

Finished benchmarking commit (10d9ecd): comparison url.

Summary: This benchmark run did not return any relevant results.

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

@rustbot label: -perf-regression