Panics are too noisy

Currently each failed lsp request will open a notification, which makes panics annoying more than what they are. Specially with panics in semantic highlighting, the corner of screen becomes unusable. I suggest raising a single notification with a message like "There was a panic. (In which request isn't really important for people) r-a may not work properly until reload. Please report it." and become silently broken in subsequent panics. If current behavior is useful for debugging, it can be enabled via a config option.

Aside this, a config for disabling semantic highlighting in ra-fixtures (which is very cool, normally) is useful for debugging panics (if there isn't already any).

Start by tracing how failed LSP requests produce notifications, then inspect the semantic-highlighting path and existing configuration handling. Check whether ra-fixtures already supports disabling semantic highlighting. Done means one useful panic notification, silent subsequent panics, and a documented opt-in debugging mode if needed.