Merge pull request #4618 from ESMCI/update-mvk-config

- Updates MVK SystemTest to be configurable via testmod
- Updates SystemTests documentation
- Refactors testmod 
- Adds ability to generate documentation from `Config` class

Test suite: n/a
Test baseline: n/a
Test namelist changes: n/a
Test status: n/a

Fixes #4592 
User interface changes?:
Update gh-pages html (Y/N)?:

.github/workflows/testing.yml

@@ -118,6 +118,8 @@ jobs:
           # from 'entrypoint.sh', create and activate new environment
           create_environment ${{ matrix.python-version }}
 
+          pip install -r test-requirements.txt
+
           # GitHub runner home is different than container
           cp -rf /root/.cime /github/home/
 
@@ -162,6 +164,8 @@ jobs:
           CIME_DRIVER: ${{ matrix.driver }}
           CIME_TEST_PLATFORM: ubuntu-latest
         run: |
+          pip install -r test-requirements.txt
+
           export CIME_REMOTE=https://github.com/${{ github.event.pull_request.head.repo.full_name || github.repository }}
           export CIME_BRANCH=${GITHUB_HEAD_REF:-${GITHUB_REF##*/}}