Split a separate codecs target off of :video_jni
Split a separate codecs target off of :video_jni

This will allow clients to include only the software codecs they need
rather than being forced to bundle them all.

- libjingle_peerconnection_jni keeps its allow_poison for now, until
  dependent targets bundle their own codecs explicitly.
- native_api_codecs and native_api_video lose their allow_poison
  because dependent targets are already bundling codecs explicitly.
- libjingle_peerconnection_metrics_default_jni and
  native_api_peerconnection lose their allow_poison because they
  were not actually poisoned.

legacy_hwcodecs_jni and default_video_codec_factory_jni exist for
clients that want to continue bundling the same codecs they get by
default today.

Bug: webrtc:7925
Change-Id: Idf853a6bc77f43decd35ad2a0f467937fec8f8b5
Reviewed-on: https://webrtc-review.googlesource.com/c/108221
Reviewed-by: Sami Kalliomäki <b9debeb8943b89663e00c95863751401cba91c9a@webrtc.org>
Commit-Queue: Jonathan Yu <53511739ffbf37996986922e276a03226eb89d41@chromium.org>
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#25564}
TimothyGu/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,TimothyGu/libilbc