Add E2E tests for AppProject synchronization between principal and managed agent

[jgwest]

#175 added support for AppProject synchronization, but no E2E tests were contributed as part of that PR, and the E2E test framework had yet to be contributed via #211.

Now that #211 is available and running as part of PRs, we can now fill in the E2E test gaps, by contributing AppProject synchronization tests.

Work Criteria:

• Implement new E2E tests for AppProject functionality which was previously contributed.
• Tests to live in e.g. 'test/e2e2/app_project_sync.go'
• Some example things to test:
  • Creation of an AppProject
    • 1. Create an AppProject on principal
    • 2. Ensure it is synced to managed agent
  • Modification of an AppProject
    • 1. Modify an existing AppProject
    • 2. Ensure the modifications are synced to managed agent
  • Delete an existing AppProject
    • 1. Delete an existing AppProject
    • 2. Ensure it is deleted from managed agent
• In addition to the above example, there is additional logic to verify related to '.spec.sourceNamespaces' field, see 'docs/architecture/appprojects.md' for details.
• Fix or file any bugs found