feat: make config method optional

[AAfghahi]

SUMMARY

Config method being required is currently not letting people add databases, we are making it optional until we have added functionality in the database create frontend.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TEST PLAN

ADDITIONAL INFORMATION

• Has associated issue:
• 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 #14668 (240056f) into master (4f5c537) will decrease coverage by 0.23%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #14668      +/-   ##
==========================================
- Coverage   77.54%   77.30%   -0.24%     
==========================================
  Files         958      958              
  Lines       48541    48541              
  Branches     5702     5702              
==========================================
- Hits        37640    37525     -115     
- Misses      10700    10815     +115     
  Partials      201      201              

Flag	Coverage Δ
hive	?
mysql	81.37% <ø> (ø)
postgres	81.39% <ø> (ø)
presto	?
python	81.47% <ø> (-0.45%)	⬇️
sqlite	81.01% <ø> (ø)

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

Impacted Files	Coverage Δ
superset/databases/schemas.py	99.54% <ø> (ø)
superset/db_engines/hive.py	0.00% <0.00%> (-82.15%)	⬇️
superset/db_engine_specs/hive.py	70.32% <0.00%> (-17.08%)	⬇️
superset/db_engine_specs/presto.py	83.36% <0.00%> (-6.53%)	⬇️
superset/views/database/mixins.py	81.03% <0.00%> (-1.73%)	⬇️
superset/connectors/sqla/models.py	88.40% <0.00%> (-1.70%)	⬇️
superset/db_engine_specs/base.py	88.04% <0.00%> (-0.42%)	⬇️
superset/models/core.py	89.51% <0.00%> (-0.27%)	⬇️
superset/utils/core.py	88.87% <0.00%> (-0.13%)	⬇️

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