Hdr metadata in image

This implements #106 (closed)

This implements three optional in KisImage, together with an applicator to calculate the maxcll and maxfall. It also saves and loads this to a kra file. These optionals are used to inform the gamut and tone mapping calculations when exported to a HDR10 format.

The end goal is to replace VideoHDRMetadataOptionsDialog in the ffmpeg settings, as well as setup this data for png and heif/avif and any other place we can use this data.

Todo:

• Implement the three HDR elements in KisImage, and give them ui in Image properties
• Save and Load to Kra files.
• Fix KisContentLightLevelProcessingVistor to work on frames somehow.
• Replace VideoHDRMetadataOptionsDialog with this data (tricky)
  • blocked by BUG:520669
  • works with ffmpeg 6
• Load this data from imported video.
  • Not possible: HDR metadata is codec specific, so ffprobe won't list it.
• Plug data into wayland API somehow ?
  • Too complex for this MR.
• Load from heif/avif (Untested...)
  • Saving requires patching libheif, because we need access via the cxx.h api.
• Implement export check.

Test Plan

• Load HDR image.
• Go to image->properties->HDR metadata
• Play with the toggles.
• Save kra file
• Load kra file
• Save HDR animation with FFMPEG 6.0, the hdr data will be pulled from the image properties.
• Test saving non-kra file; there should be a warning about HDR metadata.

Formalities Checklist

• I confirmed this builds.
• I confirmed Krita ran and the relevant functions work.
• I tested the relevant unit tests and can confirm they are not broken. (If not possible, don't hesitate to ask for help!)
• I made sure my commits build individually and have good descriptions as per KDE guidelines.
• I made sure my code conforms to the standards set in the HACKING file.
• I can confirm the code is licensed and attributed appropriately, and that unattributed code is mine, as per KDE Licensing Policy.
• Does the patch add a user-visible feature? If yes, is there a documentation MR ready for it at Krita Documentation Repository?
  • There's a branch waiting, might be used for other HDR documentation.