NVEnc encoder codecs Tune options are empty "none" in linux, as well as additional options field missing

Description of the feature or enhancement you'd like to see in HandBrake

In current master version in linux then selecting Nvenc encoders tune combobox has only "None" option while in windows is is populated properly. Same can be said for additional options, it is plain missing in linux yet if you use .json preset with those options set they are actually utilized.

Made a small tweak for GTK UI to properly display both then using NVEnc's codecs.

https://github.com/HomidWay/HandBrake/tree/LinuxNVENCFixes

What Operating System are you running?

Fedora linux

What version of HandBrake are you running?

1.11.2

Where did you download HandBrake from?

rpm / flatpak, both the same

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