[Lens] New color mapping to GA

[teresaalvarezsoler]

Description
After a year of technical preview for the new color mapping we haven't received any feedback that may change the current UX significantly int he future. We understand there can be improvements in the future but we feel confident to bring it to GA.

Tasks

• [Lens] Store raw values for color mapping assignments #193080 should be fixed to unblock the next steps
• Rename color mapping labels as described in [Lens] Integrate Borealis color palette #192848 (comment)
• Existing visualizations using the old color mapping will be automatically migrated to the new color mapping. The migration should work like this:
  • The "Compatibility palette" will be migrated to the "Legacy" palette
  • The various existing gradient palettes (temperature, status etc) will be migrated to the new color mapping with a gradient mode and the gradient color steps aligned with the colors from the palette (not from specific hex color like today) to allow improved handling for light/dark mode.
• Remove the switcher and the tech preview badge
• Previous color system tests should be converted to the new palette
• Tech preview specific code should be removed
• A well written release note should be provided
• A blog post should be written

[elasticmachine]

Pinging @elastic/kibana-visualizations (Team:Visualizations)

[markov00]

blocked by #193080