Organization & documentation of app-level Test Case Suite

[janahaddad]

@uturuncoglu 's suggestion is to look at UFS WM case studies for inspiration:
https://ufs-case-studies.readthedocs.io/en/develop/index.html
& build similar documentation for our test case suite (externally to RT system)

[janahaddad]

See also recently added case studies to the SRW app: https://github.com/ufs-community/ufs-srweather-app/tree/develop/tests/WE2E/test_configs/ufs_case_studies

from EPIC Quarterly meeting June 13: