libavformat/mpegts: expose raw packet size

We cannot easily determine if an mpeg TS's packet size is DVHS, FEC
or so on, for that we need to expose the internal raw_packet_size
field.

Signed-off-by: Leandro Dorileo <leandro.maciel.dorileo@intel.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
rpl: Dont fill the index with entries that failed to be parsed

Fixes use of uninitialized memory
Fixes: msan_uninit-mem_7fd10a199a3c_6204_landing.rpl
Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>