feat(sshtunnel): add configuration for SSH_TIMEOUT

[hughhhh]

SUMMARY

Add an additional configuration for setting SSH_TIMEOUT for sshtunnel package. The config allows us to set the timeout on individual packets.

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 #24369 (03f86ba) into master (cd78ccb) will decrease coverage by 10.87%.
The diff coverage is 90.90%.

❗ Current head 03f86ba differs from pull request most recent head 9af87e9. Consider uploading reports for the commit 9af87e9 to get more accurate results

@@             Coverage Diff             @@
##           master   #24369       +/-   ##
===========================================
- Coverage   69.05%   58.18%   -10.87%     
===========================================
  Files        1903     1903               
  Lines       74537    74199      -338     
  Branches     8108     8110        +2     
===========================================
- Hits        51468    43173     -8295     
- Misses      20957    28914     +7957     
  Partials     2112     2112               

Flag	Coverage Δ
hive	54.05% <87.87%> (+0.25%)	⬆️
mysql	?
postgres	?
presto	53.97% <87.87%> (+0.25%)	⬆️
python	60.93% <87.87%> (-22.40%)	⬇️
sqlite	?
unit	54.46% <84.84%> (+0.25%)	⬆️

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

Impacted Files	Coverage Δ
...end/src/components/Datasource/DatasourceEditor.jsx	65.35% <ø> (ø)
superset-frontend/src/dashboard/actions/hydrate.js	2.04% <ø> (ø)
...erset-frontend/src/profile/components/fixtures.tsx	100.00% <ø> (ø)
superset/models/sql_lab.py	75.10% <0.00%> (-3.48%)	⬇️
superset/views/base.py	61.90% <ø> (-15.31%)	⬇️
superset/connectors/sqla/models.py	74.89% <81.25%> (-14.75%)	⬇️
...tend/src/components/Datasource/CollectionTable.tsx	82.11% <100.00%> (+0.75%)	⬆️
...nd/src/dashboard/components/nativeFilters/utils.ts	72.05% <100.00%> (+1.74%)	⬆️
superset/config.py	91.40% <100.00%> (-0.53%)	⬇️
superset/extensions/ssh.py	68.29% <100.00%> (+0.79%)	⬆️
... and 3 more

... and 296 files with indirect coverage changes

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