core(config): Throw an error if an onlyX filter is an empty array

[OronW]

Summary
This is a bugfix, which fixes this issue:
#14986
Logic fix and relevant unit tests were added.

Description
TLDR: Throw an Error In case and empty array of onlyCategories / onlyAudits is passed

In the case an empty array of onlyCategories is passed, all categories are filtered (as only 0 categories are to be kept).
This results in an unexpected behavior, as an empty array might be interpreted as "don't filter anything".
Since passing an empty array serves no use, an error is thrown.

TBD
The original issue referred to throwing an error also for the case in which audits is left empty after filtering, however empty/missing audits is being handled in following code, and throwing an error breaks this logic.
Throwing an error for empty audits also breaks 30 tests.

I would suggest not changing any audits logic, or logging a warning only.