Fuzzer support

[qarmin]

Recently I tried to create simple automatic fuzzer to test project to find crashes/leaks but I got few problems.

Current patch (feel free to take it, fix/modify and create PR) - 0002-Ruff-fuzzer.patch.txt

• lint_stdin is not available from outside of module (pub mod diagnostics; fixes it)
• Cannot easy create settings with all available rules enabled - for testing purposes I enabled for_rules constructor for non test builds and I set there random one rule
• Looks that lint_stdin finds different problems that default ruff command(probably lint_path).
  When testing, after a while(fuzzer need to start to test longer inputs) I see in terminal messages

error: Failed to converge after 100 iterations.

This indicates a bug in `ruff`. If you could open an issue at:

    https://github.com/charliermarsh/ruff/issues/new?title=%5BInfinite%20loop%5D

...quoting the contents of `-`, along with the `pyproject.toml` settings and executed command, we'd be very appreciative!

but when I check file with ruff 256274.py --fix(256274.py.zip) command, then I got parse error message

error: Failed to parse pp/256274.py: invalid syntax. Got unexpected token ';' at line 1 column 7

I already used fuzzer to minimize test case from #3425, so I can confirm that it works(at least partially)

After applying patch, to run fuzzer you need to run this commands

cargo install cargo-fuzz
cd ruff
cargo +nightly fuzz run fuzz_target_1

[charliermarsh]

We added fuzzer support recently (#4822).