Removing VCMCodecDataBase::Codec and VideoCodingModule::Codec.

This CL brings us one step closer to removing CodecDatabase and
GenericEncoder, by removing the static VCM::Codec(). Codec specific
methods are moved to video_encoder.cc (they already belonged to this
class) and getting default generic codec settings has been moved to a
test specific file.

This CL also makes video_encoder.h pass style guide and lint checks,
since these checks are triggered with the new video_encoder.cc file.

BUG=webrtc:8064

Review-Url: https://codereview.webrtc.org/2993923002
Cr-Commit-Position: refs/heads/master@{#19303}

PRESUBMIT.py

@@ -17,7 +17,6 @@ import sys
 CPPLINT_BLACKLIST = [
   'tools_webrtc',
   'webrtc/api/video_codecs/video_decoder.h',
-  'webrtc/api/video_codecs/video_encoder.h',
   'webrtc/examples/objc',
   'webrtc/media',
   'webrtc/modules/audio_coding',