More structure constructor parameters should accept python sequences

[cmbruns]

For example:

• xr.InstanceCreateInfo.enabled_api_layer_count/enabled_api_layer_names should accept a sequence of strings
• xr.FrameEndInfo.layer_count/layers should accept a sequence of layers
• xr.CompositionLayerProjection.view_count/views should accept a sequence of CompositionLayerProjectionViews

Pretty much anything with both a Foo.bar_count: int and a Foo.bars: POINTER(something) member should accept a sequence as a constructor parameter.

• Also maybe HandJointLocationsEXT.joint_count/joint_locations

[cmbruns]

Initial implementation completed with today's commits.