feat: `--luma-bias` introduces frame-level luma bias to improve quality in dark scenes

Description

Issue

This is the third Merge Request from the SVT-AV1-PSY team aiming to integrate our features into mainline SVT-AV1 under the oversight of Hassene Tmar and Faouzi Kossentini. When enabled, the --luma-bias parameter enables frame-level luma bias to improve quality in dark scenes by adjusting frame-level QP based on average luminance across each frame.

Luma bias is disabled by default in this MR.

Author(s)

Gianni Rosato (@computerbuster)

Clybius

Performance impact

• quality
• memory
• speed
• 8 bit
• 10 bit
• N/A

Test set

• obj-1-fast can be found here
• other
• N/A

Merge method

• Allow the maintainer to squash and merge when PR is ready to create a 1-commit to the master branch. The maintainer will be able to fix typos / combine commit messages to create a more readable 1-commit message or use whatever is stated in the 'Description' section
• I will clean up my commits and the maintainer shall use 'rebase and merge' to the master branch