Exclude files from Searches | Mark directories as excluded

[Jerakin]

Is your feature request related to a problem? Please describe (REQUIRED):
When using "Search in Files" or "Open Asset" it often includes files I am not interested in. When I develop I usually have external libraries, test, and other data that I know I don't want to show up in any kind of search.

Describe the solution you'd like (REQUIRED):
I would like to be able to mark these directories as excluded to stop them from ending up in any "search" dialog.

Describe alternatives you've considered (REQUIRED):
Doing it manually

Additional context (OPTIONAL):
Common feature in other IDEAs however there they would also be excluded from any Language Server feature which I don't think I want here.

This is an editor only feature and would infer no change on any builds.

[vlaaad]

Idea: implement exclusion in the place where we currently support inclusion patterns.