Release v16.0.0

Merge pull request #1265 from firebase/mc/12

Update FirebaseUI to be compatible with Firebase 12

Merge pull request #1262 from firebase/further-ui-tweaks

Merge pull request #1222 from firebase/mc/fb-dep

update package.swift

Prep to publish 14.2.6 with fix for #1207 (#1213)

Fix Xcode 16 build error (#1211)

Make sure FUIAuthDelegate methods get called for Firebase 11 (#1203)

Fix Swift sample build (#1202)

Update config for GSI v7 (#1200)

Fix build regression (#1197)

* Fix build regression

* phoneauthui spm build issues

* test build fix