Remove libmedia and libstagefright dependency from extractors

- MediaSource, DataSource and MediaExtractor are moved to
  libmediaextractor so that they can be used by extractor
  implementations without depending on libmedia and libstagefright.
- XXXFactory classes has been added in order not to expose CreateXXX
  methods in libmediaextractor.
- avc_utils is moved to libstagefright_foundation since most of
  extractor implementations are relying on that.

Test: build + post submit media CTS tests
Bug: 65851881
Change-Id: I7d5cf18dd25abc10478ac3f6e7d1828ad023e3fb