Pixel format conversion improvement

[Khaoklong51]

implement --pix-format-converter which set converter to use for converting pixel format for video file input.
This implement pixel converter using built in vapoursynth resize function.

Possible value:

• ffmpeg Use ffmpeg to convert pixel format. (default)
• vs-resize Use vapoursynth built in resize function to convert pixel format.

Set --pix-format-converter vs-resize save about 100 MB in 8 to 10 bits encode and 199 MB in 10 to 8 bits encode using svt-av1 video encoder compare to --pix-format-converter ffmpeg.

Test Result:
- 8 -> 10 bits encode 1920*1080
- vs-resize
vspipe ~400 MB
svt-av1 ~1200 MB
total ~1600 MB

- ffmpeg 
vspipe ~350 MB
ffmpeg ~171 MB
svt-av1 ~1200 MB
total ~1721 MB

- 10 -> 8 bits encode 1920*816
- vs-resize 
vspipe ~270 MB
svt-av1 ~850 MB
total ~1120 MB

- ffmpeg
vspipe ~310 MB
ffmpeg ~129 MB
svt-av1 ~880 MB
total ~1319 MB

[codecov]

Codecov Report

❌ Patch coverage is 28.57143% with 45 lines in your changes missing coverage. Please review.
✅ Project coverage is 62.97%. Comparing base (bdbd47c) to head (6ec6b20).

Files with missing lines	Patch %	Lines
av1an-core/src/ffmpeg.rs	0.00%	23 Missing ⚠️
av1an-core/src/context.rs	40.00%	21 Missing ⚠️
av1an-core/src/lib.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1190      +/-   ##
==========================================
- Coverage   63.28%   62.97%   -0.31%     
==========================================
  Files          23       23              
  Lines        7315     7374      +59     
==========================================
+ Hits         4629     4644      +15     
- Misses       2686     2730      +44     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.