FS-7500: reduce CNG frames on video and move debug from mod_fsv to the core with a flag to enable it since the raw packet is not available anymore when you set DECODED READ flag

FS-7500: reverse default for CF_VIDEO_ECHO to false and now it must be enabled when desired instead of disabled when not needed

FS-7500: add switch_core_session_raw_read to put session into raw read mode without needing a local codec var (WE SHOULD REFACTOR MUCH OF switch_ivr_* to use this...) and add echo_decode_audio option to echo app

FS-7508: change vpx encoder to not re-init the whole codec, it messes it up but side effect, we need to init the encoder at 4k and scale down to aovid the vpx resize seg

FS-7500: clean up logic of encoder flow and set rules on return values and tweak some codec settings on vp8

FS-7500: add video_decoded_echo var to make the echo app decode and re-encode video frames for testing

FS-7500: add SFF_USE_VIDEO_TIMESTAMP to tell video write frame if it needs to use a timer or not for timestamps