fix: map schemes json to SequentialScheme (#17812)

[hbruch]

SUMMARY

In setupColor, json EXTRA_SEQUENTIAL_COLOR_SCHEMES schemes are mapped to SequentialScheme.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

Before:

After:

TESTING INSTRUCTIONS

1. In superset_config.py, define EXTRA_SEQUENTIAL_COLOR_SCHEMES, e.g. like

  EXTRA_SEQUENTIAL_COLOR_SCHEMES =[
    {
         "id": 'mySequentialScheme',
         "description": 'myDescription',
         "label": 'myLabel',
         "isDiverging": False,
         "colors":
          ['#dfdeeb', '#cac8dd', '#b5b2d0', '#a09dc2', 
           '#8d8ab6', '#7c79ab',
           '#6b69a0', '#5a5995', '#464889', '#2e367b']
    }
]

2. start superset
3. create a chart e.g. DeckGL polygon chart
4. In chart editor, Switch to Customize tab
5. See color dropdown which includes custom color scheme

ADDITIONAL INFORMATION

• Has associated issue: Fixes EXTRA_SEQUENTIAL_COLOR_SCHEMES result in error in color dropdown  #17812
• 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 #17813 (5050118) into master (b82da5c) will decrease coverage by 0.00%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master   #17813      +/-   ##
==========================================
- Coverage   67.17%   67.17%   -0.01%     
==========================================
  Files        1609     1609              
  Lines       64796    64797       +1     
  Branches     6855     6855              
==========================================
  Hits        43528    43528              
- Misses      19412    19413       +1     
  Partials     1856     1856              

Flag	Coverage Δ
javascript	53.90% <0.00%> (-0.01%)	⬇️

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

Impacted Files	Coverage Δ
superset-frontend/src/setup/setupColors.ts	81.81% <0.00%> (-8.19%)	⬇️

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[villebro]

LGTM, thanks for the fix!