Always show unsafe and display-only fixes in the CLI
Summary
--
This is the CLI accompaniment to #27807. The main change here is showing display-only fix diffs in
the CLI. However, display-only fixes don't have a corresponding flag like `--unsafe-fixes`, and I
thought it would be weird to show them unconditionally when we don't do the same for unsafe fixes,
so this PR also unconditionally renders unsafe fix diffs, even when that flag isn't passed. We
already emit a note about the fix being unsafe, so I think it makes sense always to show you the
fix, and make `--unsafe-fixes` enable actually applying the fix. We also don't want to apply
display-only fixes, so enabling rendering of the fixes with `--display-only-fixes` or similar would
also disagree with the semantics of the unsafe flag. I'm open to other ideas here, though.
The sub-diagnostic for display-only fixes uses a higher severity than the note for unsafe fixes and
renders in red, as shown below.
Test Plan
--
Updated existing snapshots, and some manual testing in the CLI:
TODO
