Summary:
PG15 upstream commit b073c3ccd06e4cb845e121387a43faa8c68a7b62 revoked the CREATE permission on public schema from PUBLIC. This revision allows `yb_db_admin` role to CREATE on public schema (and as an extension on all schemas, just like superuser).

The `yb_db_admin` role in YugabyteDB is a special role that allows non-superuser users to perform certain privileged operations that would typically require superuser privileges. This role is particularly important in YugabyteDB Aeon (formerly YugabyteDB Managed) environments.

PG15 revoked the create permission on public schema from `PUBLIC`, so only superuser and users under the role `pg_database_owner` has the create permission. For YugabyteDB Aeon environments `yb_db_admin` must also have this permission.
Jira: DB-15564

Test Plan:
./yb_build.sh --java-test 'org.yb.pgsql.TestPgAuthorization#testPgPublicSchemaCreateAuthorization'
./yb_build.sh --java-test 'org.yb.pgsql.TestYsqlUpgrade#migratingIsEquivalentToReinitdb'
./yb_build.sh --java-test 'org.yb.pgsql.TestYsqlDump'

Reviewers: skumar, hsunder, stiwary, smishra

Reviewed By: hsunder

Subscribers: yql

Differential Revision: https://phorge.dev.yugabyte.com/D42198