feat: add Postgres SQL validator

[betodealmeida]

SUMMARY

This PR adds a SQL validator for Postgres queries in SQL Lab. It uses the pgsanity module, which parses the query, providing syntax validation without having to talk to the database.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TEST PLAN

Create a superset_config.py:

SQLALCHEMY_DATABASE_URI = "postgresql://superset:superset@localhost/test" 

FEATURE_FLAGS: Dict[str, Any] = {
    "SQL_VALIDATORS_BY_ENGINE": {"postgresql": "PostgreSQLValidator"},
}

And tested a few queries.

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 #11538 (8dbbfb2) into master (6f2e36d) will decrease coverage by 5.65%.
The diff coverage is 54.54%.

@@            Coverage Diff             @@
##           master   #11538      +/-   ##
==========================================
- Coverage   66.62%   60.96%   -5.66%     
==========================================
  Files         873      888      +15     
  Lines       41870    43324    +1454     
  Branches     3847     3817      -30     
==========================================
- Hits        27894    26412    -1482     
- Misses      13875    16912    +3037     
+ Partials      101        0     -101     

Flag	Coverage Δ
cypress	55.36% <ø> (-0.46%)	⬇️
javascript	?
python	63.86% <54.54%> (+1.70%)	⬆️

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

Impacted Files	Coverage Δ
superset/sql_validators/__init__.py	80.00% <50.00%> (ø)
superset/sql_validators/postgres.py	50.00% <50.00%> (ø)
superset/config.py	90.07% <100.00%> (-0.08%)	⬇️
...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%)	⬇️
...et-frontend/src/components/Menu/LanguagePicker.tsx	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%)	⬇️
...components/AdhocFilterEditPopoverSqlTabContent.jsx	7.14% <0.00%> (-92.86%)	⬇️
...ntend/src/views/CRUD/annotation/AnnotationList.tsx	1.36% <0.00%> (-90.94%)	⬇️
... and 489 more

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[villebro]

I love it! LGTM, but bonus points for a test if it's not too much trouble.

[bkyryliuk]

please add unit tests