[ENHANCEMENT] Add features of SvtAv1EncApp to the library libsvtav1

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Is your feature request related to a problem? Please describe.
This fork has great new features for SvtAv1EncApp, like for example the options --dolby-vision-rpu, and --hdr10plus-json.
Unfortunately these new features are only available via SvtAv1EncApp directly and are not exposed via the library libsvtav1.

For example when using ffmpeg one would expect

ffmpeg -i input.mkv -map 0:v:0 -c:v libsvtav1 -pix_fmt + \
    -svtav1-params dolby-vision-rpu=RPU.bin:hdr10plus-json=metadata.json \
    output.mkv

to work, but it actually throws the error

[libsvtav1 @ 0x5b20cba383c0] Error parsing option dolby-vision-rpu: RPU.bin.
[libsvtav1 @ 0x5b20cba383c0] Error parsing option hdr10plus-json: metadata.json.

showing that the library is not aware of these options.

Describe the solution you'd like
All the options supported by SvtAv1EncApp should also be supported by the library libsvtav1.

Describe alternatives you've considered
The cumbersome alternative is to pipe ffmpeg's output directly to SvtAv1EncApp though this is much less flexible.