parser.rs is too big. Some functions only for error reporting and error
recovery are being moved to diagostics.rs.

tidy: Fix some more false positives for long URLs

A URL that's simply longer than 100 characters is ok regardless of context.

r? @varkor

move some functions from parser.rs to diagostics.rs

Starting with a few functions mentioned in rust-lang#60015 (comment). We might refactor parser.rs further in subsequent changes.
r? @petrochenkov

Add test not to forget resolved ICE

closes rust-lang#55499

I added the example as a test.

r? @pnkfelix

…entril

Stabilize str::as_mut_ptr

Closes rust-lang#58215