Whenever I add dependency to cabal, I have to restart VS Code

Whenever I add dependency to cabal, I have to restart VS Code so that the plugin can see it and doesn't display missing imports and other errors. `cabal build` or `killall -9 haskell-language-server-9.10.1` don't help, only restarting does.

Reproduce the issue in VS Code by adding a dependency to the Cabal configuration, then run `cabal build` and the documented HLS restart command to compare their effects. Trace how the VS Code extension notices dependency changes; done means new imports are recognized without restarting VS Code and without stale diagnostics.

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