fix: css template API response, less data

[dpgaspar]

SUMMARY

Simplifies and send less unneeded data back, on the CSS template get list REST API

TESTING INSTRUCTIONS

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 #17980 (1640525) into master (ea3a583) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 1640525 differs from pull request most recent head e73c9c3. Consider uploading reports for the commit e73c9c3 to get more accurate results

@@           Coverage Diff           @@
##           master   #17980   +/-   ##
=======================================
  Coverage   67.07%   67.08%           
=======================================
  Files        1609     1611    +2     
  Lines       64903    64919   +16     
  Branches     6868     6871    +3     
=======================================
+ Hits        43535    43548   +13     
- Misses      19502    19504    +2     
- Partials     1866     1867    +1     

Flag	Coverage Δ
hive	53.29% <ø> (ø)
mysql	82.19% <ø> (ø)
postgres	82.24% <ø> (ø)
presto	53.13% <ø> (ø)
python	82.68% <ø> (ø)
sqlite	81.92% <ø> (ø)

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

Impacted Files	Coverage Δ
.../plugins/legacy-preset-chart-nvd3/src/Bar/index.js	66.66% <ø> (ø)
...gins/legacy-preset-chart-nvd3/src/DistBar/index.js	66.66% <ø> (ø)
...ins/legacy-preset-chart-nvd3/src/DualLine/index.js	66.66% <ø> (ø)
...plugins/legacy-preset-chart-nvd3/src/ReactNVD3.jsx	0.00% <ø> (ø)
...ontend/src/dashboard/fixtures/mockNativeFilters.ts	100.00% <ø> (ø)
superset-frontend/src/explore/fixtures.tsx	70.00% <ø> (ø)
superset/css_templates/api.py	95.74% <ø> (ø)
superset-frontend/src/components/Select/Select.tsx	86.42% <100.00%> (+0.09%)	⬆️
...board/components/nativeFilters/FilterBar/index.tsx	82.96% <100.00%> (+0.12%)	⬆️
... and 1 more

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[villebro]

LGTM

[rosemarie-chiu]

🏷 2022.1