Toloka-kit

Features:
* Retries should work not only while establishing connection to server but also when transfering data
* Added functional tests against production environment
* Fixed `TemplateBuilder` structure method issue with attributes annotated by `ListBaseComponent`
* TolokaClient method names are passed in request headers. This allows usage analytics for complex features such as `clone_project` or `get_assignments` that call subsequent TolokaClient methods.
* Now you can track 11 metric types from Toloka with minimal latency.

* AsyncTolokaClient introduced (experimental)
* Streaming state storage introduced (experimental)

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Yanked due to issues found in retries functionality:
* Might raise maximum recursion depth exceptions
* Breaks `download_attachment`

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* Added `from_json` and `to_json` convenience functions to `BaseTolokaObject`
* Added docstrings for Toloka App API client part
* Supported classes with `async def __call__(...)` as streaming handlers
* `inherit_docstrings` decorator preserves `__init__` positional arguments ordering
* `TolokaClient` is now pickleable

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* Fixed an exceptions caused by returning status 204 with an empty body from API
* Fixed several bugs in toloka apps methods

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* Reverted from `PreloadingHTTPAdapter` to `HTTPAdapter`
* Fixed `get_app_items()` signature

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* Added methods to use toloka apps
* Used `PreloadingHTTPAdapter` instead of `HTTPAdapter`