1. Remove prerelease tag.
2. Add TARGET_BUILD_WIDEVINE_USE_PREBUILT to control building from source.
3. Unify config namespace to "widevine".
Bug: 251299786
Bug: 277764729
Change-Id: I2f19bcf8efd280a1a3aa86f595599d79e20b4ff4
[ Merge of go/wvgerrit/164757 ]
Modify Widevine apex configuration to add add liboemcrypto.so as
required by WV APEX.
Bug: 243699259
Test: atp v2/widevine-eng/drm_compliance
Change-Id: I136dde5d77aed4fb14737e4692153c8f3b2c701b