Add more authenticated end-to-end tests

[annieli555]

Context

Add additional baseline authenticated tests using the new authentication flow introduced in f464e74. Also adds some test helpers to create a new (empty) project, create an new (empty) character, and interact with Firestore.

The new tests include (as discussed in #195 (comment)):

• Ensuring that a project is saved to the (emulated) cloud after being edited
• Ensuring that a custom character is saved to the (emulated) cloud of being edited

I also added a test to verify that character references in projects are updated when a character name changes, as this was not tested when I added the feature in #817, due to authenticated tests not being supported at the time. But now it is supported!

Related issues

• Closes Support authenticated end to end tests #195

Verification

Checklist

• Verify tests pass in CI Investigate test timeout issue (this seems to be an existing bug, recent PRs are also encountering test timeouts)

[amyjko]

This is a great new set of tests! And much needed.

The timeout is curious. Maybe it's imposed on PR workflows run by people not collaborators on a project? The docs say that timeouts should be 60 minutes.