chore: Audit E2E tests for color schemes in Dashboard and Explore

[geido]

SUMMARY

Enhanced the Cypress tests for the color schemes to:

• Test the selection of a color scheme for a Dashboard when saving and editing
• Test the color schemes are applied
• Test the selection of a color scheme for viz types

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

[codecov]

Codecov Report

Merging #20807 (ac03654) into master (802b69f) will decrease coverage by 11.49%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           master   #20807       +/-   ##
===========================================
- Coverage   66.35%   54.85%   -11.50%     
===========================================
  Files        1767     1767               
  Lines       67332    67332               
  Branches     7144     7144               
===========================================
- Hits        44675    36934     -7741     
- Misses      20829    28570     +7741     
  Partials     1828     1828               

Flag	Coverage Δ
hive	53.13% <ø> (ø)
javascript	52.11% <ø> (ø)
mysql	?
postgres	?
presto	53.03% <ø> (ø)
python	57.76% <ø> (-23.72%)	⬇️
sqlite	?
unit	50.45% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
superset/utils/dashboard_import_export.py	0.00% <0.00%> (-100.00%)	⬇️
superset/key_value/commands/update.py	0.00% <0.00%> (-88.89%)	⬇️
superset/key_value/commands/delete.py	0.00% <0.00%> (-85.30%)	⬇️
superset/key_value/commands/delete_expired.py	0.00% <0.00%> (-80.77%)	⬇️
superset/dashboards/commands/importers/v0.py	15.62% <0.00%> (-76.25%)	⬇️
superset/datasets/commands/update.py	25.00% <0.00%> (-69.05%)	⬇️
superset/datasets/commands/create.py	29.41% <0.00%> (-68.63%)	⬇️
superset/datasets/commands/importers/v0.py	24.03% <0.00%> (-67.45%)	⬇️
superset/views/datasource/utils.py	26.66% <0.00%> (-66.67%)	⬇️
superset/reports/commands/execute.py	25.37% <0.00%> (-66.05%)	⬇️
... and 278 more

📣 Codecov can now indicate which changes are the most critical in Pull Requests. Learn more

[jinghua-qa]

LGTM!