support a NOT operator in queries

[OmarTawfik]

Suggestion from @0xcompose:

I've thought that queries could have logical operator NOT. It could be really cool for linters. Often linters check absence of something in source code. For example finding all mutative functions and checking that there is NO event emitted, so error/warning must be shown.

We should evaluate how this impacts other query operators, and whether it should just check for optional fields, or be able to handle more complex sub-patterns.