fix: css templates modal cleanup: keep modal open on error, utilize useEffect

[riahk]

SUMMARY

• Handles errors on save/update so modal does not close when an error is encountered
• utilizes useEffect hook for initialization to reduce API requests

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TEST PLAN

Manual Test:

1. Create or update css template without network connectivity
2. Attempt to save
3. Confirm that an error toast is thrown and the modal does not close

ADDITIONAL INFORMATION

• Has associated issue:
• Changes UI
• Requires DB Migration.
• Confirm DB Migration upgrade and downgrade tested.
• Introduces new feature or API
• Removes existing feature or API

[codecov-io]

Codecov Report

Merging #12360 (6b218a0) into master (24fccdb) will decrease coverage by 15.87%.
The diff coverage is 0.00%.

@@             Coverage Diff             @@
##           master   #12360       +/-   ##
===========================================
- Coverage   67.05%   51.17%   -15.88%     
===========================================
  Files        1001      473      -528     
  Lines       49380    16881    -32499     
  Branches     5033     4333      -700     
===========================================
- Hits        33110     8639    -24471     
+ Misses      16142     8242     -7900     
+ Partials      128        0      -128     

Flag	Coverage Δ
cypress	51.17% <0.00%> (-0.06%)	⬇️
javascript	?
python	?

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

Impacted Files	Coverage Δ
...d/src/views/CRUD/csstemplates/CssTemplateModal.tsx	5.26% <0.00%> (-67.19%)	⬇️
...uperset-frontend/src/dashboard/util/dnd-reorder.js	0.00% <0.00%> (-100.00%)	⬇️
...rset-frontend/src/dashboard/util/getEmptyLayout.js	0.00% <0.00%> (-100.00%)	⬇️
...dashboard/components/resizable/ResizableHandle.jsx	0.00% <0.00%> (-100.00%)	⬇️
.../src/dashboard/util/getFilterScopeFromNodesTree.js	0.00% <0.00%> (-93.48%)	⬇️
...set-frontend/src/views/CRUD/alert/ExecutionLog.tsx	11.76% <0.00%> (-88.24%)	⬇️
...src/dashboard/components/gridComponents/Header.jsx	10.52% <0.00%> (-86.85%)	⬇️
superset-frontend/src/components/IconTooltip.tsx	13.33% <0.00%> (-86.67%)	⬇️
...rc/dashboard/components/gridComponents/Divider.jsx	13.33% <0.00%> (-86.67%)	⬇️
...end/src/SqlLab/components/ExploreResultsButton.jsx	8.00% <0.00%> (-84.00%)	⬇️
... and 867 more

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