Workspace diagnostics

[MichaReiser]

Add support for workspace-wide diagnostics in addition to showing diagnostics for open files only. Default to workspace-wide diagnostics, but with an option to switch to open file diagnostics.

Work items

• Initial support for workspace diagnostics using workspace/diagnostic endpoint ([ty] Initial support for workspace diagnostics ruff#18939)
• Fix VS Code not clearing diagnostics in non-workspace mode ([ty] Initial support for workspace diagnostics ruff#18939 > "Test Plan" > "VS Code") ([ty] Avoid stale diagnostics for open files diagnostic mode ruff#19273)
• Consider open virtual files (might requires Track open files in server #619) ([ty] Add virtual files to the only project database ruff#19322)
• Add support using publish diagnostics notification (low priority) ¹
• Consider Jupyter Notebooks (low priority)

Footnotes

1. This is a low priority mainly because clients like VS Code, Zed and (soon) Neovim supports the workspace/diagnostic (pull diagnostic) endpoint. ↩

[dhruvmanila]

Add support using publish diagnostics notification (low priority)

I think we should only do this if there are user requests for it otherwise it might get complicated to support both the push and pull model for workspace diagnostics.

Consider Jupyter Notebooks (low priority)

Merging this into #173

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Closing this as completed. I've opened a separate issue for the one remaining task which is related to performance.