mediacodec->mediacodec+hal_omx{,_server,_client}

(breaks vendor blobs, will have to be regenerated
after this CL)

This moves mediacodec to vendor so it is replaced with
hal_omx_server. The main benefit of this is that someone
can create their own implementation of mediacodec without
having to alter the one in the tree. mediacodec is still
seccomp enforced by CTS tests.

Fixes: 36375899
Test: (sanity) YouTube
Test: (sanity) camera pics + video
Test: check for denials
Change-Id: I31f91b7ad6cd0a891a1681ff3b9af82ab400ce5e