Added support for custom adapter hooks

[timlehr]

Summarize your change.

Rebased PR #1711

This adds support for attributing custom hooks to adapters and executing them with hook_function_argument_map being passed along through the adapter IO functions.

Describe the reason for the change.

I added two custom hooks to the OTIO AAF adapter (OpenTimelineIO/otio-aaf-adapter#43), allowing for embedding of media essence into the resulting AAF. This was needed to facilitate just-in-time DNXHR transcoding of the media for the AAF creation and adding a certain level of control and flexibility to the feature.

These features to the core are required in order to properly pass the hook argument map along to potential custom hooks run by the adapter. I tried to work with _FEATURE_MAP instead of creating a new version of the Adapter schema in order to minimize the impact of this change, while adding the necessary changes to facilitate custom hooks for adapters.

Reference associated tests.

tests/test_adapter_plugin.py
tests/test_hooks_plugins.py

[timlehr]

@ssteinbach I finally had some time to revive #1711. Please have a look when you find some time. Thank you! 🙏