test speed of ffio

• aiming to test the speed of Python wrapper for FFmpeg-C-API compared with pure FFmpeg-C-API
• The test condition:
  • AMD x86_64 (16 cpu cores),
  • Ubuntu 18.04, gcc, FFmpeg-6.0, Python 3.10.
  • video: 29.97fps, 1920*1080p, 2M/s
• running 1 loop of decode-ffio is composed of decode-C(purely call FFmpeg-C-API to get 1 frame) and decode-py-convertor(convert C image frame to python format, numpy default). Same to encoder items.
• The table below shows that decoding 1 frame costs 15.84ms in average, in which 1.49ms is used to convert decoded image in C format(unsigned char *) to python format(numpy, etc.). encoding 1 frame costs 11.96ms in average, in which 2.03ms is used to do C-py format conversion.

functions	average cost time(ms)	max cost time(ms)	min cost time(ms)
decode-ffio	15.84	42.28	8.08
decode-C	14.34	40.43	7.00
decode-py-convertor	1.49	2.63	1.02
encode-ffio	11.96	22.65	10.37
encode-C	9.92	18.41	9.13
encode-py-convertor	2.03	4.49	1.05