UM.isUserTypeEnabled @TestApi

Make this API available for CTS tests. This way, for device-side tests,
you can tell tests to be skipped if their purpose involves creating a
profile for which the device isn't eligible anyway.

Test: N/A
Bug: 255793314
Bug: 255377177
Bug: 241298595
Bug: 257125968
Change-Id: I3a6d93f8092e327c9d6073e68e57d1eab2cfa127