Fixing CoreML in Java (#16231)
### Description
The name of the flag we set when compiling the JNI binding to enable the CoreML EP changed at some point in the past. This PR fixes it by updating the flag in the JNI. I also added a quick smoke test for the CoreML provider to make sure it doesn't crash and can be enabled.
### Motivation and Context
All the EPs should work as expected in Java. Fixes #16230.
