Reduce amount of tests we run in CI

[ostinru]

In #136 it is planned to add 20+ Github Action Steps. And we agreed (#113) that we should keep number of tests we run under control. This PR reduces amount of test steps we run:

1. Remove sanity tests group (few tests here)
2. Remove jdbc test group (no tests in the group)
3. Run 'features' and 'gpdb' tests together - test groups shares 80% of the tests

   Group	Tests count
   features total	329
   gpdb total	321
   features & gpdb	264
   features only	65
   gpdb only	57