chore: deprecate /superset/fetch_datasource_metadata mig to API v1

[dpgaspar]

SUMMARY

Continuing the effort on deprecating all /superset/ REST API endpoints
Deprecates /superset/fetch_datasource_metadata replaced by the already existing /api/v1/dataset/<id>

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 #22102 (ac2eeb8) into master (5b67e07) will decrease coverage by 1.26%.
The diff coverage is 50.00%.

❗ Current head ac2eeb8 differs from pull request most recent head 4541927. Consider uploading reports for the commit 4541927 to get more accurate results

@@            Coverage Diff             @@
##           master   #22102      +/-   ##
==========================================
- Coverage   67.12%   65.86%   -1.27%     
==========================================
  Files        1831     1831              
  Lines       69993    69994       +1     
  Branches     7570     7570              
==========================================
- Hits        46983    46099     -884     
- Misses      21045    21930     +885     
  Partials     1965     1965              

Flag	Coverage Δ
hive	52.84% <0.00%> (-0.01%)	⬇️
mysql	78.40% <100.00%> (+<0.01%)	⬆️
postgres	78.46% <100.00%> (+<0.01%)	⬆️
presto	52.74% <0.00%> (-0.01%)	⬇️
python	78.94% <100.00%> (-2.64%)	⬇️
sqlite	76.93% <100.00%> (+<0.01%)	⬆️
unit	?

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

Impacted Files	Coverage Δ
superset-frontend/src/SqlLab/actions/sqlLab.js	62.85% <0.00%> (ø)
superset/datasets/api.py	87.39% <ø> (ø)
superset/views/core.py	75.94% <100.00%> (+0.01%)	⬆️
superset/tables/schemas.py	0.00% <0.00%> (-100.00%)	⬇️
superset/columns/schemas.py	0.00% <0.00%> (-100.00%)	⬇️
...set/advanced_data_type/plugins/internet_address.py	16.32% <0.00%> (-79.60%)	⬇️
superset/utils/pandas_postprocessing/boxplot.py	20.51% <0.00%> (-79.49%)	⬇️
superset/charts/post_processing.py	11.76% <0.00%> (-77.95%)	⬇️
...perset/advanced_data_type/plugins/internet_port.py	18.75% <0.00%> (-77.09%)	⬇️
superset/utils/pandas_postprocessing/rolling.py	21.87% <0.00%> (-68.75%)	⬇️
... and 55 more

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more

[villebro]

LGTM + tested to work as expected (it took me a while to figure out how to trigger this 😆). One more nail in the coffin! ⚰️🔨

[dpgaspar]

Took me a while also, should have added an "how to test" on the PR description, will do that next time. Thank you once more for the review