feat(auth): Support for creating tenant-scoped session cookies

[hiranya911]

• Upgraded some Maven plugins to latest to avoid some issues with Jacoco code coverage reporting in older versions.
• Cleaned up the Builder APIs in FirebaseAuth and TenantAwareFirebaseAuth.
• Moved session cookie creation and verification APIs to AbstractFirebaseAuth so they are inherited by both subclasses of this API.
• Implemented support for verifying tenant-scoped session cookies (by passing a tenant ID to the respective FirebaseTokenVerifier).
• Implemented support for creating tenant-scoped session cookies (by verifying the ID token locally which also matches tenant IDs)

RELEASE NOTE: Exposing createSessionCookie() and verifySessionCookie() methods from the TenantAwareFirebaseAuth class.

[lahirumaramba]

Thank you! LGTM!

Should we get the new docs reviewed?

[hiranya911]

Those are existing docs. We are just moving them from FirebaseAuth to AbstractFirebaseAuth. I'm also debating whether to merge this PR now or finish off the v7 work first. I'll figure it out next week.