[Feature Request]: Add Go APIs for dynamically using Java SchemaTransforms via expansion service

### What would you like to happen?

Starting Beam 2.44.0, Java expansion service can automatically identify SchemaTransforms available in the classpath and offer them for expansion by remote SDKs. We also added Python APIs for dynamically discovering and using such SchemaTransforms.

Proposal: https://s.apache.org/easy-multi-language
Python API: https://github.com/apache/beam/blob/a460eb14ab5b1d05f0dfeb1afd6b427215478d96/sdks/python/apache_beam/transforms/external.py#L319

We should add a similar API to Go SDK. We are in the process of developing a number of SchemaTransforms for existing Java I/O connectors so this will basically make such I/O connectors available for Go SDK automatically.

### Issue Priority

Priority: 2

### Issue Component

Component: sdk-go