smartencoder: clean up and extend accepted formats: add H265 and use avc3/hev1 variants
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Add support for H265
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Don't overwrite original codec_data / streamheader in the output caps, but instead allow them to change and send them to the combiner at the right moment: encoder caps, reencoded GOP, original caps, original GOP(s), and potentially encoder caps and rencoded last GOP.
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For H264 / H265, force usage of a format with inband SPS / PPS (avc3 / hev1), this is cleaner than misadvertising avc1, hvc1 and some muxers like mp4mux will actually advertise both differently.
Unfortunately, while mp4 supports updating the codec_data and using avc1 with no in-band SPS / PPS updates, it turns out some decoders (eg chrome / firefox) don't handle this particularly well and stop decoding after the reencoded GOP. We could expose a switch to force usage of avc1 / hvc1 nevertheless, but for now stick to requiring that the parser output SPS / PPS in-band with config-interval=-1 (that has not changed)