Add R-Tree overload of beginRecording

[mattleibow]

Description of Change

Add the R-Tree overload of SkPicture::beginRecording.

Only the construction and destruction of the sole implementation of SkBBHFactory (the SkRTreeFactory class) is exposed. This is really an opaque type in skia and clients would create their own implementations if they wanted. However, this PR does not provide the API to do this since it is fairly complicated and not many use cases. It can be added later.

SkiaSharp Issue

Related to mono/SkiaSharp#2372

API Changes

sk_canvas_t* sk_picture_recorder_begin_recording_with_bbox_hierarchy(sk_picture_recorder_t*, const sk_rect_t*, sk_bbh_factory_t*);

sk_rtree_factory_t* sk_rtree_factory_new(void);
void sk_rtree_factory_delete(sk_rtree_factory_t*);

Behavioral Changes

None.

Required SkiaSharp PR

Requires mono/SkiaSharp#2889

PR Checklist

• Rebased on top of skiasharp at time of PR
• Changes adhere to coding standard
• Updated documentation