Additional options in MediaPipe Face Mesh and Holistic

• MediaPipe Face Mesh
  • Added an refine_landmarks option in the Solution APIs to further improve landmarks around eyes and lips, and output additional landmarks around the irises.
  • Released the Attention Mesh ML model that enables refine_landmarks.
• MediaPipe Holistic
  • Added the enable_segmentation and smooth_segmentation option in the Solution APIs, previously only available in MediaPipe Pose.