Move mediacodec to vendor partition.

Test: Camera, Photos, YouTube, and Play Movies apps.
Test: With CtsMediaTestCases.apk installed,
adb shell am instrument -e size small -w
'android.media.cts/android.support.test.runner.AndroidJUnitRunner'

Bug: 35328855
Change-Id: I0f36683b531fc645835a94e449996e5b44d0a3de