Python: Event Streaming (#2482)

* Add `RustType.Application` and `PythonType.Application` variants

* Use `RustType.Application` for event streaming symbols

* Call symbol provider to get `Receiver` type instead of hardcoding

* Add Python specific event streaming symbol provider

* Add event streaming wrapper generator

* Generate correct type information for event streaming types

* Add `CapturePokemon` operation to Python Pokemon service

* Add `InternalServerError` variant to all event streaming errors

* Use `PythonServerCargoDependency` for PyO3Asyncio imports

* Return an attribute error instead of panicking in `IntoPy` impls of wrappers

* Add `Sync` bound to `new` methods of wrappers

* Revert "Add `InternalServerError` variant to all event streaming errors"

This reverts commit b610cb27c7532102e3a3ec15a59da6c56b60c318.

* Add `PythonServerEventStreamErrorGenerator` to generate Python specific error types for unions

* Try to extract error type or inner type from incoming streaming value and ignore the value otherwise for now

* Allow missing type-stubs for `aiohttp`

* Propogate modelled errors through stream

* Raise modelled exceptions rather than sending through stream

* Allow senders from Python side to raise modelled exceptions

* Update `EventStreamSymbolProviderTest` to use `Application` type instead of `Opaque` type

* Fix `ktlint` issues

* Group up common variables in `codegenScope`

* Document `RustType.Application`

* Format `codegen-server-test/python/model/pokemon.smithy`

* Use `tokio-stream` crate instead of `futures` crate

* Use a better error message if user tries to reuse a stream

* Add some details about event streams to example Pokemon service

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Co-authored-by: Matteo Bigoi <1781140+crisidev@users.noreply.github.com>