Add -AskipDirs that is like -AskipDefs

[nitspat]

When running checkers, I would like to exclude generated classes. However, our generated classes use the same package structure and names as the remaining, hand-written, code.

Enhancement Request:
I would like to be able to exclude generated classes by their directory, e.g.
-skipDirs=".*target\generated-sources\.*"

Thias issue relates to:
https://stackoverflow.com/questions/76662206/excluding-nullnesschecker-by-directory-not-package