Support tags

[kostja]

Allow to tag tests with multiple tags. Add ./test-run --tags list,of,tags which only runs a test if it matches one of the tags.

The idea of this feature is that we'll be able to tag tests by code areas which they cover, and developers will be able to quickly re-run tests which affect their work domain most.

This feature supersedes --long option of test-run.

[Totktonada]

We had a talk with @Gerold103 and agreed that it would be nice to use tags for gh-xxxx issue marks and exclude those ugly gh-xxxx from test names.