fix: Fix Big Query API for POST w/ no parameters

[hughhhh]

SUMMARY

Put in a quick fix to pull data from credentials_info key, and check for configuration_method instead of parameters.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

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 #14822 (386259f) into master (dfe030b) will decrease coverage by 0.23%.
The diff coverage is 69.23%.

@@            Coverage Diff             @@
##           master   #14822      +/-   ##
==========================================
- Coverage   77.62%   77.38%   -0.24%     
==========================================
  Files         962      962              
  Lines       49172    49174       +2     
  Branches     6184     6184              
==========================================
- Hits        38169    38055     -114     
- Misses      10801    10917     +116     
  Partials      202      202              

Flag	Coverage Δ
hive	?
javascript	72.44% <ø> (ø)
mysql	81.62% <69.23%> (-0.01%)	⬇️
postgres	81.65% <69.23%> (-0.01%)	⬇️
presto	?
python	81.73% <69.23%> (-0.45%)	⬇️
sqlite	81.26% <69.23%> (-0.01%)	⬇️

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

Impacted Files	Coverage Δ
superset/db_engine_specs/bigquery.py	90.15% <0.00%> (-0.69%)	⬇️
superset/databases/schemas.py	98.72% <81.81%> (+<0.01%)	⬆️
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	88.08% <0.00%> (-1.67%)	⬇️
superset/db_engine_specs/base.py	87.90% <0.00%> (-0.41%)	⬇️
superset/models/core.py	89.70% <0.00%> (-0.27%)	⬇️
superset/utils/core.py	88.91% <0.00%> (-0.13%)	⬇️

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