Use new `Diagnostic` functionality for Ruff rules

[ntBre]

It's a bit late in the process, but it seemed useful to write up a tracking issue for the remaining TODOs before we can take advantage of our new Diagnostic infrastructure in Ruff. This is primarily focused on the full output format, which is where the new functionality like multiple annotations will be visible. We've already switched over the concise and a few other formats without any user-visible changes.

In brief, the remaining tasks are to switch Ruff over to the new full-format rendering code in ruff_db, update our caching code to preserve all of the information in the new diagnostics instead of the legacy subset (or sidestep this by avoiding the cache entirely in those cases, as we ended up doing), and then actually use some of the new functionality in real lint rules. The first of these has been broken into a few subtasks to make it easier for review.

• Move full diagnostic rendering to ruff_db #19415
  • Allow hiding the diagnostic severity in ruff_db #19644
  • Hide empty snippets for full-file diagnostics #19653
  • [ty] Remap Jupyter notebook cell indices in ruff_db #19698
• Don't cache files with diagnostics #19869
• Set Annotation::is_file_level in affected lint rules #19688
• Use new diagnostic functionality #17203

[ntBre]

I mostly wanted to track the stack of rendering PRs and then caching. The remaining tasks seem well-covered by their own issues.