Autocomplete Improvements

[rcosta358]

This PR improves the autocomplete suggestions by:

• Not suggesting ghosts/states from different classes (aliases are fine)
• Implementing annotation-specific suggestions
• Implementing trigger characters (" and .)
• Suggesting ghosts/states after this. or old(this).
• Suggesting parameters in method and parameter level refinements
• Suggesting the variable we are refining (doesn't work very reliably because of the last point mentioned in the future work section)

Future Work

• Not suggest return unless we are in a method level refinement (still shows for field refinements)
• Autocomplete for @ExternalRefinementsFor (similarly to the autocomplete VS Code provides in imports)
• Have autocomplete work even in the presence of LiquidJava errors (e.g., when an error occurs, subsequent variables are not added to the context and therefore are not suggested)

[CatarinaGamboa]

rebase first, i think there are some changes in server right? maybe i'm confusing

[CatarinaGamboa]

why dont we need this? maybe rebase

[rcosta358]

I left that dependency commented out for testing the verifier locally, where I'd manually build and place the verifier jar in the language server. However, by simply running mvn install in the verifier, the dependency is automatically updated locally, as long as the version numbers match, so it's just unnecessary.

[rcosta358]

The rebase was already performed.