Serve json numpy encoding

[jeffkinnison]

This update handles a TypeError thrown by ludwig/serve.py when JSON-encoding numpy arrays with starlette.responses.JSONResponse objects. It includes:

• A NumpyJSONResponse class that replaces the default JSON encoder with ludwig.utils.data_utils.NumpyEncoder
• Updated NumpyJSONResponse instances in ludwig/serve.py
• Unit tests for both NumpyEncoder and NumpyJSONResponse

[github-actions]

Unit Test Results

       5 files  ±0         5 suites  ±0   2h 4m 8s ⏱️ + 9m 13s
2 943 tests +2  2 894 ✔️ +2    49 💤 ±0  0 ❌ ±0 
8 704 runs  +6  8 542 ✔️ +6  162 💤 ±0  0 ❌ ±0 

Results for commit 9f65aa2. ± Comparison against base commit a2bce0e.

[tgaddair]

Nice!