fix: database schema selector on import data

[dpgaspar]

SUMMARY

Small refactor on CSV, Excel, Columnar database data import. Make javascript reusable

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

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 #21759 (852c553) into master (d1a6f0e) will decrease coverage by 0.74%.
The diff coverage is 72.72%.

❗ Current head 852c553 differs from pull request most recent head 956ad44. Consider uploading reports for the commit 956ad44 to get more accurate results

@@            Coverage Diff             @@
##           master   #21759      +/-   ##
==========================================
- Coverage   66.85%   66.10%   -0.75%     
==========================================
  Files        1800     1800              
  Lines       68957    68957              
  Branches     7335     7335              
==========================================
- Hits        46098    45582     -516     
- Misses      20966    21482     +516     
  Partials     1893     1893              

Flag	Coverage Δ
hive	52.93% <ø> (ø)
mysql	?
postgres	?
presto	52.83% <ø> (ø)
python	79.91% <ø> (-1.55%)	⬇️
sqlite	76.80% <ø> (ø)
unit	51.05% <ø> (ø)

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

Impacted Files	Coverage Δ
superset-frontend/src/embedded/index.tsx	0.00% <0.00%> (ø)
...ackages/superset-ui-switchboard/src/switchboard.ts	100.00% <100.00%> (ø)
superset/datasets/commands/update.py	25.00% <0.00%> (-69.05%)	⬇️
superset/datasets/commands/create.py	31.25% <0.00%> (-68.75%)	⬇️
superset/datasets/commands/bulk_delete.py	33.33% <0.00%> (-53.34%)	⬇️
superset/datasets/columns/commands/delete.py	44.11% <0.00%> (-52.95%)	⬇️
superset/datasets/metrics/commands/delete.py	44.11% <0.00%> (-52.95%)	⬇️
superset/datasets/dao.py	44.21% <0.00%> (-50.35%)	⬇️
superset/sql_validators/postgres.py	50.00% <0.00%> (-50.00%)	⬇️
superset/datasets/commands/delete.py	48.57% <0.00%> (-48.58%)	⬇️
... and 28 more

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[villebro]

LGTM