Schema name should be configurable

**Is your feature request related to a problem? Please describe.**
Different companies have rules and standards about where they install extensions. As a result, most extensions support `CREATE EXTENSION SCHEMA `.

Unfortunately, AGE specifies the schema name in the control file, and as a result, it cannot be installed anywhere else: `ERROR: extension "age" must be installed in schema "ag_catalog"`

**Describe the solution you'd like**
I'd like to see AGE support configurable installation schema via the standard Postgres syntax.