Missing semantic tokens after editing in large files

[Colengms]

If you have a very large file (>5000 lines), an edit may result in temporarily losing semantic tokens up to about 5000 lines before the edits and beyond 5000 lines after the edits. Semantic tokens are restored once a full parse occurs, which occurs when saving the file or switching between documents.

In the short term, we could mitigate the issue by preserving stale tokens instead of clearing them (this would require doing some merging and fixing up positions, at lease for the tokens after the edits). However, to keep all of the semantic tokens in the file always up to date, the following issue may be a prerequisite: #7759

[Colengms]

I believe this may have been addressed with #7759