Render concise snapshots in linter tests

[ntBre]

Summary

This is a quick implementation of the idea in #19900 (comment). Especially as we start using new diagnostic features, it seems like a good idea to keep an eye on the concise output format as well as the full. This PR just appends a second rendering of the diagnostics in our rule snapshots in the concise format. The concise message is typically reused in the other output formats too, so this kind of gives us a bit of coverage for all the output formats.

I noticed that some of our concise messages are still quite long. That might be another good class of diagnostic to use new features for. Some explanatory pieces might fit better as sub-diagnostics, now that we're not limited to a single line in the default case.

Adding these lines (and adding a let binding for emitter) is the only code change:

ruff/crates/ruff_linter/src/test.rs

Lines 371 to 383 in 1fbb88f

	if !diagnostics.is_empty() {
	output.extend(b"## Concise Output\n");
	}
	emitter
	.with_show_source(false)
	.with_show_fix_diff(false)
	.emit(
	&mut output,
	diagnostics,
	&EmitterContext::new(&FxHashMap::default()),
	)
	.unwrap();

Test Plan

Existing snapshots. Again, I clicked through these individually, but very, very quickly

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

✅ ecosystem check detected no linter changes.

[MichaReiser]

Thanks for looking into this.

IMO, this contains too much redundant information and will only increase the noise when making changes to our tests. That's why I'd prefer a more granular opt in to testing the concise output