Add SpatialAnnotation API and SpatialTrackingOptions Builder for SpatialAnnotation.startTracking to ARCore.

This CL introduces the SpatialAnnotation API to track 3D physical objects based on camera image buffers. It adds the SpatialAnnotation trackable class, along with SpatialAnnotationTrackingOptions and related enums for configuring tracking.

RelNote: "Introduced the `SpatialAnnotation` API for tracking 3D physical geometries and objects. Added `SpatialAnnotationTrackingOptions` and its corresponding builder pattern to configure spatial tracking via camera image buffers."

Bug: 543096679
Bug: 545231260
Test: ./gradlew :xr:arcore:...
Change-Id: I918ce6aae1d433c9b55173bc320e924d4a332c8d