[DON'T MERGE] Port #[cfg] and #[cfg_attr] trace attributes to the new attribute parsers

[JonathanBrouwer]

Code is still very ugly in places, no need to review yet. Made the PR for perf

[JonathanBrouwer]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

@rustbot label: +S-waiting-on-perf

[JonathanBrouwer]

@bors try cancel

[rust-bors]

Try build cancelled. Cancelled workflows:

• https://github.com/rust-lang/rust/actions/runs/20303060187

[JonathanBrouwer]

@bors try @rust-timer queue

[rust-timer]

This pull request is already queued and waiting for a try build to finish.

[rust-bors]

☀️ Try build successful (CI)
Build commit: 42e640c (42e640c5f0c710e5113f19d4652388db81a0cff9, parent: 58b270bebef86316f70174d5a1ea4eb19ef91b62)

[rust-timer]

Queued 42e640c with parent 58b270b, future comparison URL.
There are currently 0 preceding artifacts in the queue.
It will probably take at least ~1.0 hours until the benchmark run finishes.