feat(add Netezza database): Add IBM Netezza support

[abhishekjog]

SUMMARY

Add support for IBM Netezza Performance Server (aka Netezza)

TESTING INSTRUCTIONS

Install Superset
Add Database with "netezza+nzpy://user:password@host:5480/database". Test that the database is added successfully.
Create Dataset. Check that all schema and tables are listed in drop down. We have checked correct queries are fired in netezza backend logs.
Try running queries, create charts etc.

ADDITIONAL INFORMATION

• Has associated issue: Add support for IBM Netezza #15452
• 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 #15450 (2bb7c62) into master (9967a5f) will decrease coverage by 0.23%.
The diff coverage is 88.88%.

@@            Coverage Diff             @@
##           master   #15450      +/-   ##
==========================================
- Coverage   77.78%   77.55%   -0.24%     
==========================================
  Files         966      969       +3     
  Lines       49629    49916     +287     
  Branches     6314     6314              
==========================================
+ Hits        38606    38711     +105     
- Misses      10822    11004     +182     
  Partials      201      201              

Flag	Coverage Δ
hive	?
mysql	81.66% <88.88%> (-0.05%)	⬇️
postgres	81.67% <88.88%> (-0.06%)	⬇️
presto	?
python	81.76% <88.88%> (-0.50%)	⬇️
sqlite	81.30% <88.88%> (-0.06%)	⬇️

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

Impacted Files	Coverage Δ
superset/db_engine_specs/netezza.py	88.88% <88.88%> (ø)
superset/db_engines/hive.py	0.00% <0.00%> (-82.15%)	⬇️
superset/db_engine_specs/trino.py	59.72% <0.00%> (-35.02%)	⬇️
superset/app.py	63.49% <0.00%> (-24.19%)	⬇️
superset/db_engine_specs/hive.py	69.20% <0.00%> (-18.20%)	⬇️
superset/exceptions.py	90.47% <0.00%> (-8.23%)	⬇️
superset/db_engine_specs/presto.py	83.36% <0.00%> (-6.95%)	⬇️
superset/databases/commands/create.py	88.23% <0.00%> (-3.93%)	⬇️
superset/connectors/connector_registry.py	83.33% <0.00%> (-2.95%)	⬇️
superset/dashboards/commands/importers/v0.py	89.94% <0.00%> (-2.92%)	⬇️
... and 37 more

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[villebro]

Thanks for the contribution! Please fix the linting error, after that I think this is good to go.

[john-bodley]

@abhishekjog could you also add/update the documentation?

[abhishekjog]

@abhishekjog could you also add/update the documentation?

yes. I had raised a separate PR, which is now merged.