Relatively large PR which introduces Workers RPC support for Python. The aim is to make it easy to call functions defined in other Python and JS Workers, to do this all arguments are converted to/from JS where appropriate.

The implementation relies on a number of wrappers as well as conversion functions:

• The binding env object is wrapped via the handler decorator, it gets wrapped in a class that intercepts calls to Fetcher bindings (i.e. env.ServiceBinding) and then another class that intercepts calls made on that binding. All arguments passed to these calls are wrapped in a call to serialize_to_js and the returned value from the call is wrapped in a call to serialize_to_python.
• The serialize_to_python and serialize_to_js functions convert Python and JS arguments to JS and Python respectively. These mostly use Pyodide's to_js and to_py but with some improvements and restrictions.
• Arguments received by WorkerEntrypoints also get converted. This is done in the code that manages the entrypoint classes and already intercepts calls.

All of this is supported by a test suite which attempts to send/receive both from and to Python, as well as from and to JS.

Test Plan

$ bazel run @workerd//src/workerd/server/tests/python:python-rpc_development@