change: Migrate credentials to use google-auth-library (#2466)

* Convert Service account, refresh token, and compute engine types to use google-auth

* Validate credential files

* update tests

* Update tests

* Remove obsolete unit tests

* fix package.json

* clean up comments

* fix integration tests

* fix integration tests

* fix auth client init process

Author: lahirumaramba

package-lock.json

@@ -209,6 +209,7 @@
     "@firebase/database-types": "1.0.5",
     "@types/node": "^22.0.1",
     "farmhash-modern": "^1.1.0",
+    "google-auth-library": "^9.14.2",
     "jsonwebtoken": "^9.0.0",
     "jwks-rsa": "^3.1.0",
     "node-forge": "^1.3.1",