Merge changes from vscode-ccls

I've done a lot of improvements to vscode-ccls extension:
- refactoring
- linting and CI
- correct restart, lazy mode
- and other smaller changes

https://github.com/MaskRay/vscode-ccls

I think this project will benefit if you cherry-pick all changes. (Or maybe replace current extension code and rename all ccls occurences to cquery)