Annotation context is a visualizer component source

Annotation context is a visualizer component source

Previously, the visualizer UI around annotation context was fairly inconsistent and confusing. The visualizer component-mapping UI now shows when a field uses annotation context and allows users to opt in or out explicitly.

TODO(andreas): Add screenshot.

Blueprints can also request annotation context explicitly:

import rerun as rr
import rerun.blueprint as rrb
from rerun.blueprint.encodings import ComponentSourceKind, VisualizerComponentMapping

view = rrb.Spatial2DView(
    overrides={
        "points": rr.Points2D.from_fields().visualizer(
            mappings=[
                VisualizerComponentMapping(
                    target="Points2D:colors",
                    source_kind=ComponentSourceKind.AnnotationContext,
                ),
            ]
        ),
    }
)

For a general overview of component mappings see component mappings. For a guide about annotation context see annotation context.

Under the hood we now resolve annotation context more rigoriously & consistently, which led to some subtle changes in behavior, see TODO(andreas): insert link.