Async filters are not awaited when with_context or with_environment is set

[jg-rp]

The async filter interface (new in version 1.9.0) falls apart when a class-based filter defining filter_async also sets with_context or with_environment to True.

This is due to our use of functools.partial to partially apply context and environment arguments. Subsequently causing hasattr(func, "filter_async") to return False when inspecting the filter at evaluation time.