SAST - Add support for a base directory or include directory

Proposal

Currently there is only the ability to exclude paths from SAST scans using the SAST_EXCLUDED_PATHS variable. However there are use cases where customers may have more than 1 application in a project and would like to use parallel:matrix to scan each of those applications in their own jobs.

In those case it would make sense to instead set a base path and or include paths from which to scan.