[Python] Allow specifying endpoint_url when using utility function pyarrow.fs.resolve_s3_region

### Describe the enhancement requested

Integration tests can mock s3 using https://pypi.org/project/moto/. If an integration test uses mock s3 to test with "mock-test-bucket" calls to `pyarrow.fs.resolve_s3_region()` will raise an exception saying the bucket doesn't exist because it tries to actually query s3.

**Feature request:** Add a parameter to be able to optionally specify the endpoint url
`pyarrow.fs.resolve_s3_region(endpoint_override="http://localhost:3000")`

### Component(s)

Python