chore: Refined fgAccent (light mode), fixed missing return in fg (light mode)

[ichik]

Description

tl;dr Preserving more color in fgAccent when the seed doesn't pass the contrast check, more saturated and pure color for better harmony. Also fixed fg that missed a return for achromatic seeds rule.

Fixes #22699

Media

New on the left, current on the right

Screen.Recording.2023-05-25.at.12.03.21.mov

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Chore (housekeeping or task changes that don't impact user perception)

How Has This Been Tested?

• Manual

Test Plan

Initial POC refinement, no testing necessary

Checklist:

Dev activity

• 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 made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• PR is being merged under a feature flag

QA activity:

• Test plan has been approved by relevant developers
• Test plan has been peer reviewed by QA
• Cypress test cases have been added and approved by either SDET or manual QA
• Organized project review call with relevant stakeholders after Round 1/2 of QA
• Added Test Plan Approved label after reveiwing all Cypress test