Export a usable Python implementation via shared library (#1476)

This PR add several functionalities to the Python/Rust code-generation, making it usable for models that are not using Streaming and Union shapes.

    * Export codegenerated shapes as shared library that can be imported by the Python interpreter.
    * Add complete end-to-end testing running in CI.
    * Register signals and handle workers processes lifecycle.
    * Use a custom SymbolProvider to override non-primitive types that are exposed to Python.
    * Implement support for DateTime.
    * Cast Python exception into Rust error types.
    * End to end testing suite with a Rust client calling a real Python server.