This CL extracts the ivf file writer from `TestEncodedImageCallback`
into separate .cc|.h files. Improve the `EncodedImageFileWriter` to
support SVC that output ivf for all decode targets.
EXAMPLE: Encode with VP9 L3T3_KEY, the outputs:
output-VP9-L3T3_KEY-L0T0.ivf
output-VP9-L3T3_KEY-L0T1.ivf
output-VP9-L3T3_KEY-L0T2.ivf
output-VP9-L3T3_KEY-L1T0.ivf
output-VP9-L3T3_KEY-L1T1.ivf
output-VP9-L3T3_KEY-L1T2.ivf
output-VP9-L3T3_KEY-L2T0.ivf
output-VP9-L3T3_KEY-L2T1.ivf
output-VP9-L3T3_KEY-L2T2.ivf
Bug: webrtc:15210
Change-Id: Iba46c897a7b783bb4b79ec18715e901476cb9f55
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/309280
Reviewed-by: Erik Språng <sprang@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Jianhui J Dai <jianhui.j.dai@intel.com>
Cr-Commit-Position: refs/heads/main@{#40363}
