Add placeholder code for latest baseline changes

[adhilto]

🗣 Description

Add placeholder code for:

• GWS.COMMONCONTROLS.15.2v0.3
• GWS.COMMONCONTROLS.18.1v0.3
• GWS.COMMONCONTROLS.18.2v0.3
• GWS.COMMONCONTROLS.18.3v0.3
• GWS.COMMONCONTROLS.18.4v0.3

Deleted:

• GWS.DRIVEDOCS.7.1v0.3
• GWS.CHAT.5.1v0.3 (and renumbed the old 6.1 and 6.2)

💭 Motivation and context

Closes #483.

Note: #444 and #473 track what still needs to be done.

🧪 Testing

Manually tested and updated unit tests.

✅ Pre-approval checklist

• [x] This PR has an informative and human-readable title.
• [x] Changes are limited to a single goal - eschew scope creep!
• [x] If applicable, All future TODOs are captured in issues, which are referenced in the PR description.
• [x] The relevant issues PR resolves are linked preferably via closing keywords.
• [x] All relevant type-of-change labels have been added.
• [x] I have read and agree to the CONTRIBUTING.md document.
• [x] These code changes follow cisagov code standards.
• [x] All relevant repo and/or project documentation has been updated to reflect the changes in this PR.
• [x] Tests have been added and/or modified to cover the changes in this PR.
• [x] All new and existing tests pass.

✅ Pre-merge Checklist

• [x] This PR has been smoke tested to ensure main is in a functional state when this PR is merged.
• [x] Squash all commits into one PR level commit using the Squash and merge button.

✅ Post-merge Checklist

• [x] Delete the branch to clean up.
• [x] Close issues resolved by this PR if the closing keywords did not activate.