chore: set Snowflake user agent

[betodealmeida]

SUMMARY

Set a user agent header in the Snowflake DB Engine Spec indicating the request is coming from Superset.

I also fixed the Databricks user agent, the get_extra_params method was returning the incorrect payload.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

N/A

TESTING INSTRUCTIONS

Added unit tests.

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 #22432 (2f7b179) into master (fa919f3) will decrease coverage by 11.17%.
The diff coverage is 87.50%.

❗ Current head 2f7b179 differs from pull request most recent head befcb84. Consider uploading reports for the commit befcb84 to get more accurate results

@@             Coverage Diff             @@
##           master   #22432       +/-   ##
===========================================
- Coverage   66.90%   55.72%   -11.18%     
===========================================
  Files        1850     1850               
  Lines       70692    70704       +12     
  Branches     7752     7752               
===========================================
- Hits        47294    39402     -7892     
- Misses      21382    29286     +7904     
  Partials     2016     2016               

Flag	Coverage Δ
hive	52.46% <25.00%> (-0.01%)	⬇️
mysql	?
postgres	?
presto	52.35% <25.00%> (-0.01%)	⬇️
python	57.78% <87.50%> (-23.46%)	⬇️
sqlite	?
unit	50.94% <87.50%> (+0.02%)	⬆️

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

Impacted Files	Coverage Δ
superset/db_engine_specs/hive.py	64.56% <0.00%> (-22.79%)	⬇️
superset/db_engine_specs/databricks.py	65.71% <100.00%> (+0.75%)	⬆️
superset/db_engine_specs/snowflake.py	64.77% <100.00%> (+1.86%)	⬆️
superset/utils/dashboard_import_export.py	0.00% <0.00%> (-100.00%)	⬇️
superset/tags/core.py	4.54% <0.00%> (-95.46%)	⬇️
superset/key_value/commands/update.py	0.00% <0.00%> (-90.91%)	⬇️
superset/key_value/commands/delete.py	0.00% <0.00%> (-87.88%)	⬇️
superset/key_value/commands/delete_expired.py	0.00% <0.00%> (-84.00%)	⬇️
superset/dashboards/commands/importers/v0.py	15.62% <0.00%> (-76.25%)	⬇️
superset/datasets/commands/create.py	30.61% <0.00%> (-69.39%)	⬇️
... and 284 more

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