Add test stage to GitHub Actions builds

[jasercion]

The pipeline should run the Fermitools test suite (unit tests, agn thread tests(?), and Tom's likelihood memory tests), parse the results, present them, and allow use of the test stage as a toggle-able blocker for build uploads.

[JamesAmrhein]

Status :
The pipeline should:

• run the Fermitools test suite:
  • unit tests, Completed - JSA
  • agn thread tests, In progress -JoeA - reimplementing tests to use smaller/faster queries/file sizes
  • Tom's likelihood memory tests, In progress -TomS -updating fermitools-test-scripts-data to include new test data
• parse the results, present them, Completed - JSA
• allow use of the test stage as a toggle-able blocker for build uploads. Deferred -JSA since the current GitHub Action that builds the conda package NEEDS to have it uploaded to Anaconda for it to pass on meta info to other workflows

Current workflow can be found at :
https://github.com/fermi-lat/ScienceTools/actions/workflows/main-ci.yml

[jasercion]

Test stage has been added, ST-AGN-thread tests incorporated, only outstanding tests are Tom's memory tests

[JamesAmrhein]

Current Status:
dev builds: Runs the following test suites: ST-unit-output , agn thread tests and python import tests.
rc/main builds: : Runs the dev test suites AND the FermiPy test suite.

TODO: Tom's performance tests will be moved to a second round of testing improvements that will include running Nestor's thread notebooks as additional tests.