Partly addresses rust-lang#71209.

delay_span_bug bumps error_count after checking treat_err_as_bug

Co-Authored-By: varkor <github@varkor.com>

…ipping, r=estebank"

This reverts commit 46a8dce, reversing
changes made to f28e387.

On `FnDef` type annotation suggestion, use fn-pointer output

Address the last point in rust-lang#71209.

…en-mir, r=eddyb

normalize field projection ty to fix broken MIR issue

Fixes rust-lang#71344

r? @eddyb

…dling, r=eddyb

Fix off by one in treat err as bug

`-Ztreat-err-as-bug` doesn't work properly with delay_span_bug.

r? @eddyb

remove obsolete comment

Not sure if it's better to have an outdated comment or no comment at all (made obsolete by 2b9fea1).

Revert rust-lang#71372 ("Fix #! (shebang) stripping account space issue").

While rust-lang#71372 fixed some of the problems `#!`-stripping had, it introduced others:
* inefficient implementation (`.chars().filter(...).collect()` on the entire input file)
  * this also means the length returned isn't always correct, leading to e.g. rust-lang#71471
* it ignores whitespace anywhere, stripping ` # ! ...` which isn't a valid shebang
  * the definition of "whitespace" it uses includes newlines, which means even `\n#\n!\n...` is stripped as a shebang (and anything matching the regex `\s*#\s*!\s*`, and not followed by `[`, really)
* it's backward-incompatible but didn't go through Crater

Now, rust-lang#71487 is already open and will solve all of these issues. But for running Crater, and just in case rust-lang#71487 takes a bit longer, I decided it's safer to just revert rust-lang#71372.

This will also make rust-lang#71372's diff clearer, as it will start again from the original whitespace-unaware version.

r? @petrochenkov