Fixes #9010. `wagtail.documents.widgets` is no longer reliably imported on startup now that the chooser widget is constructed within wagtail.documents.views.chooser instead, so the telepath adapter wasn't getting register. This meant that DocumentChooserBlocks in StreamField were using the base chooser implementation, which didn't include customisations such as populating the title field from the file upload field. Fix this by making ChooserViewSet responsible for registering the telepath adapter.
Fixes #8989. The previous fix #9004 failed for custom document models because ChooserViewset assigns an internal name for the ChooserBlock class based on the model name, and if this is anything other than Document it won't match the name DocumentChooserBlock that it's exposed under in wagtail.documents.blocks. Fix this by replacing the `block_class` property with a `get_block_class` method that lets us specify the class name. As a bonus, user code that defines chooser blocks no longer has to directly hack the `__module__` attribute.
- fix some broken refs that were lost in the migration to markdown files
- use lower_snake_case for all internal refs (most follow this convention)
- release process sub-section in docs should be named release schedule instead
- Use inline code for `Locale` and `TranslatableMixin` headers to be consistent with other classes in the page
- Move `locale` and `translation_key` of `TranslatableMixin` to its own "Database fields" section
- Add missing periods in Page.update_aliases parameter description
Fixes #8989. Now that DocumentChooserBlock is constructed dynamically via wagtail.documents.viewsets.chooser, we need to explicitly set its `__module__` attribute so that the result of calling `deconstruct()` for migrations points back to the wagtail.documents.blocks module.
Also update the documentation for defining custom choosers, and add tests for deconstructing the other chooser blocks.
