Make pgsched compile in parallel with objectstore by default

Currently the Postgres Scheduler DB code is being compiled only on request using a cmake flag combination: -DCTA_USE_PGSCHED:Bool=true -DDISABLE_ORACLE_SUPPORT:BOOL=OFF and these explicitly exclude compilation of the Objectstore implementation.

As a result, in the current CI, any changes made in the CTA code are never being tested to compile with the Postgres Scheduler DB. We need to enable the compilation of the Postgres Scheduler DB by default in parallel to the Objectstore implementation in order to avoid the currently unnecessary regular maintenance work done on the code in order to catch up with the rest of the developments.