Move libmediandk and libcamera2ndk headers

Move libmediandk and libcamera2ndk headers into their module
and export them from there.  Also move them to the same path
relative to the export as used in the NDK, media/ for
libmediandk and camera/ for libcamera2ndk.

Test: builds
Change-Id: I0b424e0e48bfb5e2b762694a97d799de08f5dda3
(cherry picked from commit 7e8d4ba5)