fix(Dashboard): Retain colors when color scheme not set

[geido]

SUMMARY

This PR does the following:

• It fixes an issue for which colors would sometimes not keep their consistency when leaving and revisiting the Dashboard.
• It fixes an issue for which charts original color schemes were not tracked making falling back to their origin color scheme impossible when removing the color scheme from the Dashboard.
• It attempts to fix and re-enable skipped E2E tests that are critical for the coverage of the color consistency implementation.

BEFORE

Color.Consistency.Test.mp4

AFTER

Color.Consistency.Test.1.mp4

TESTING INSTRUCTIONS

1. Open a Dashboard with a color scheme and shared label colors
2. Edit the Dashboard properties and remove the color scheme
3. After applying the changes, verify that shared label colors are still respected
4. For charts that do not share labels, verify their original color scheme is respected
5. Save and exit the Dashboard by going to the Dashboard lists
6. Come back again to the same Dashboard you just saved
7. Make sure colors haven't changed from the previous state

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API