Add camera.metadata@3.3

To be used by camera.device@3.4; unfortunately the versioning is
now skewing since no metadata additions were needed for device@3.3

Includes the earlier-added control.afSceneChange entry.

Test: hidl-gen, hidl-doc, builds
Bug: 64847201
Change-Id: I341a018a7eccf63758e356e9b426a41b575ade9f