nvenc, amdvce: rework all user presets/options

[psyke83]

Description

nvenc: rework all user presets/options

• Presets: remove deprecated presets; add new p1-p7 presets; set "p4" as default.
• Tuning: add new tuning options; set "ull" as default.
• Rate control: remove deprecated options; set "cbr" as default.
• Web UI: keep case consistency (NVEnc -> NVENC, all drop-down options as lowercase);
  ensure all default options are clearly indicated.
• Coder: clarify H264-only status; keep default to "auto".
• Ensure all default presets are correctly identical between C++ and HTML code.
• To improve future compatibility, refer to all possible options via same
  definitions used in ffmpeg code via nvenc headers.
• Docs: update with new profile and tuning options.

amdvce: rework all user presets/options

• Quality - fix different values used between codecs; set "balanced" as default.
• Rate control: remove "auto"; set "vbr_latency" as default.
• Web UI: keep consistency (AMD AMF -> AMF, all drop-down options as lowercase);
  ensure all default options are clearly indicated.
• Coder: clarify H264-only status; keep default to "auto".
• Ensure all default presets are correctly identical between C++ and HTML code.
• To improve future compatibility, refer to all possible options via same
  definitions used in ffmpeg code via AMF headers.
• Docs: update with new options and descriptions.

Screenshot

Issues Fixed or Closed

Closes #211

TODO

• Requires new FFMPEG binaries + NVIDIA headers present for Sunshine to build
• Verify if build breaks on platforms that don't distribute NVENC headers
• Fix merge conflicts after FFmpeg 5 and pre-built CBS #509 is merged

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Dependency update (updates to dependencies)
• Documentation update (changes to documentation)
• Repository update (changes to repository files, e.g. .github/...)

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated the in code docstring/documentation-blocks for new or existing methods/components

Branch Updates

LizardByte requires that branches be up-to-date before merging. This means that after any PR is merged, this branch
must be updated before it can be merged. You must also
Allow edits from maintainers.

• I want maintainers to keep my branch updated

[KuleRucket]

What is the reason for VBR as default? Nvidia recommends CBR for cloud gaming/streaming.

https://docs.nvidia.com/video-technologies/video-codec-sdk/nvenc-video-encoder-api-prog-guide/#recommended-nvenc-settings

EDIT: wrong link to recommendations section

[ReenigneArcher]

I just have a minor suggestion to docs

[psyke83]

@ReenigneArcher:

I've also updated the AMF encoder, as I noticed that the "Quality" setting differs between codecs and therefore requires special handling.

An outstanding issue with this PR is that it may break macos due to the nv/amf headers not being available. Would you prefer that I hardcode the definitions that needs these headers (and thus lose future-proofing compatibility), or exclude the sections via something like #ifndef __APPLE__?

If opting for the first option seems best, future-proofing could be improved if we make <libavcodec/nvenc.h> available to Sunshine's build include path as well.