Cleanup unused diagnostic emission methods

[GuillaumeGomez]

Part of #153099.

To remove lint_level, we need to remove all functions calling it. One of them is TyCtxt::node_span_lint, so removing it.

r? @JonathanBrouwer

[rustbot]

HIR ty lowering was modified

cc @fmease

[rustbot]

JonathanBrouwer is currently at their maximum review capacity.
They may take a while to respond.

[rustbot]

Some changes occurred in src/tools/clippy

cc @rust-lang/clippy

[GuillaumeGomez]

PR is not ready, we need to figure out why the tracking is currently broken in clippy:

--- tests/ui/track-diagnostics-clippy.stderr
+++ <stderr output>
 error: casting to the same type is unnecessary (`u32` -> `u32`)
   --> tests/ui/track-diagnostics-clippy.rs:LL:CC
... 2 lines skipped ...
    |             ^^^^^^^^ help: try: `a`
    |
-   = note: -Ztrack-diagnostics: created at clippy_lints/src/casts/unnecessary_cast.rs:LL:CC
+   = note: -Ztrack-diagnostics: created at compiler/rustc_middle/src/lint.rs:LL:CC
    = note: `-D clippy::unnecessary-cast` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::unnecessary_cast)]`
... 18 lines skipped ...
 error: aborting due to 2 previous errors

You can run this (specific) test with:

TESTNAME=track-diagnostics-clippy ./x.py test src/tools/clippy/ --stage 1

[JonathanBrouwer]

r=me if ci green & you agree with my commit

[GuillaumeGomez]

@bors r=JonathanBrouwer rollup

[rust-bors]

📌 Commit e01a7e7 has been approved by JonathanBrouwer

It is now in the queue for this repository.