feat: Add loading state to sqllab save/overwrite dataset modal

[jfrag1]

SUMMARY

Overwriting datasets in particular can take a long time to run since it makes a request to PUT /api/v1/datasets/{id}?override_columns=true, which will execute the updated query on the DB. Requests that can take this long should have a loading indicator to let the user know something is happening and not broken.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

Before:

After:

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 #23697 (ceb6cd1) into master (b39edc1) will decrease coverage by 0.01%.
The diff coverage is 16.66%.

❗ Current head ceb6cd1 differs from pull request most recent head 4a0421c. Consider uploading reports for the commit 4a0421c to get more accurate results

@@            Coverage Diff             @@
##           master   #23697      +/-   ##
==========================================
- Coverage   66.30%   66.29%   -0.01%     
==========================================
  Files        1922     1922              
  Lines       74048    74054       +6     
  Branches     8104     8104              
==========================================
+ Hits        49094    49095       +1     
- Misses      22882    22887       +5     
  Partials     2072     2072              

Flag	Coverage Δ
javascript	54.12% <16.66%> (-0.01%)	⬇️

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Impacted Files	Coverage Δ
...d/src/SqlLab/components/SaveDatasetModal/index.tsx	50.00% <16.66%> (-2.28%)	⬇️

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[eschutho]

Nice!