fix: Big Query additional parameters field doesn't keep value

[lyndsiWilliams]

SUMMARY

This was fixed by converting the query into a URI params string.

SCREENSHOTS

TESTING INSTRUCTIONS

From the Superset home page:

• Hover over "Data" in the upper navigation bar
• Click "Database"
• Click the "+ Database" button below the navigation bar and to the right
• Create a new BigQuery database and add an additional parameter
• Click the edit button and observe that the additional parameters field now keeps the value

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 #16161 (c7cf47b) into master (606a7bf) will decrease coverage by 0.00%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master   #16161      +/-   ##
==========================================
- Coverage   76.82%   76.81%   -0.01%     
==========================================
  Files         996      996              
  Lines       52940    52942       +2     
  Branches     6732     6734       +2     
==========================================
  Hits        40670    40670              
- Misses      12045    12047       +2     
  Partials      225      225              

Flag	Coverage Δ
javascript	71.19% <0.00%> (-0.01%)	⬇️

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

Impacted Files	Coverage Δ
...c/views/CRUD/data/database/DatabaseModal/index.tsx	44.15% <0.00%> (-0.24%)	⬇️

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