[Auth] Add integration tests for multi-tenancy support

[sam-gc]

The tests are going to fail in CI until we update the firebase-tools dependency version number, once the new changes roll out in that repo.

[changeset-bot]

⚠️ No Changeset found

Latest commit: d44fc4c

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[yuchenshi]

Awesome

[google-oss-bot]

Binary Size Report

Affected SDKs

No changes between base commit (53a9263) and head commit (b4d1547).

Test Logs

• Base (53a92639): https://github.com/firebase/firebase-js-sdk/actions/runs/1318049810
• Head (b4d15472): https://github.com/firebase/firebase-js-sdk/actions/runs/1321243525

[google-oss-bot]

Size Analysis Report

Affected Products

No changes between base commit (53a9263) and head commit (b4d1547).

Test Logs

• Base (53a9263): https://github.com/firebase/firebase-js-sdk/actions/runs/1318049810
• Head (b4d1547): https://github.com/firebase/firebase-js-sdk/actions/runs/1321243525

[lisajian]

Nit: newline?