[WOR-1482] Move remainder of Workspaces-owned code out of src/pages/workspaces

[cahrens]

Jira Ticket: https://broadworkbench.atlassian.net/browse/WOR-1482

This completes the work started in #4622

1. WorkspaceDashboard code has been moved to src/workspaces/dashboard, except for the routing page file src/pages/workspaces/WorkspaceDashboard.ts, DashboardPublic, and DashboardAuthContainer.
2. WorkspaceMigration code has been moved to src/workspaces/migration, except for the routing page file src/pages/workspaces/WorkspaceMigration.ts.
3. There are no references to src/pages/workspace in src/workspaces.
4. CODEOWNERS file is updated accordingly.

This is what is left under src/pages/workspaces:

[cahrens]

The entry at line 22 is non-recursive, so it captures our very minimal Page classes.

[cahrens]

@blakery FYI that in the last 2 commits I moved some code back to src/pages/workspaces. Talking to @nawatts and @msilva-broad, our desire is to have the page "wrapper" code that includes TopBar and Footer under src/pages. I moved that code back where it was simple to do so, but I am leaving the refactoring to allow such a split in WorkspaceContainer and WorkspacesList for a future change, as it's going to require some substantial work. That would also likely be a good time to do some tsx conversion.

It's also good to keep things that rely on authStore (DashboardAuthContainer) out of src/workspaces….

[sonarcloud]

Quality Gate passed

The SonarCloud Quality Gate passed, but some issues were introduced.

8 New issues
0 Security Hotspots
76.5% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud