fix(bigquery): Properly display errors for BigQuery DBs

[Antonio-RiveroMartnez]

SUMMARY

This PR is fixing the wrong error messages we are seeing with BigQuery after we introduced these changes: #22024 .

Initially we were trying to get rid of bigquery error: section in the message, so we decided to split the exception message. However, the engine is NOT adding such section into the message, instead it's just returning: 400 Syntax error: ... for example, and it's us the ones adding that in this method: extract_error_message from the BaseEngineSpec class.

So, these proposed changes are not splitting the message, just getting the first line (if multiple), and we keep the bigquery error: section in it. We could also override the extract_error_message in BigQueryEngineSpec to remove that section, however, I'd like to be consistent with all our other engines.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

Before:

After:

TESTING INSTRUCTIONS

1. Open SQL Lab and force a Syntax error when querying a BigQuery DB
2. Error message should display properly

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 #22349 (fbfe33e) into master (d2b76a8) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master   #22349      +/-   ##
==========================================
- Coverage   66.85%   66.85%   -0.01%     
==========================================
  Files        1847     1847              
  Lines       70560    70560              
  Branches     7737     7737              
==========================================
- Hits        47173    47171       -2     
- Misses      21380    21382       +2     
  Partials     2007     2007              

Flag	Coverage Δ
hive	52.53% <0.00%> (ø)
mysql	77.95% <0.00%> (ø)
postgres	78.02% <0.00%> (ø)
presto	52.42% <0.00%> (ø)
python	81.23% <100.00%> (-0.01%)	⬇️
sqlite	76.48% <0.00%> (ø)
unit	50.91% <100.00%> (-0.01%)	⬇️

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Impacted Files	Coverage Δ
superset/db_engine_specs/bigquery.py	81.68% <100.00%> (-1.00%)	⬇️

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