Port #[register_tool] to the new attribute system

[jdonszelmann]

@rustbot blocked on #146652

[bors]

☔ The latest upstream changes (presumably #146862) made this pull request unmergeable. Please resolve the merge conflicts.

[bors]

☔ The latest upstream changes (presumably #147019) made this pull request unmergeable. Please resolve the merge conflicts.

[rust-log-analyzer]

The job aarch64-gnu-llvm-20-1 failed! Check out the build log: (web) (plain enhanced) (plain)

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[RUSTC-TIMING] rustc_parse test:false 17.333
error: unused import: `LimitInvalid`
 --> compiler/rustc_attr_parsing/src/attributes/crate_level.rs:2:54
  |
2 | use crate::session_diagnostics::{ExpectedSingleWord, LimitInvalid};
  |                                                      ^^^^^^^^^^^^
  |
  = note: `-D unused-imports` implied by `-D warnings`
  = help: to override `-D warnings` add `#[allow(unused_imports)]`

[bors]

☔ The latest upstream changes (presumably #147345) made this pull request unmergeable. Please resolve the merge conflicts.