Add instrumentation for the lib/pq posgres driver package

[MrAlias]

• README
• End-to-end tests
• Unit tests
• Code complete
• Documented

[codecov-commenter]

Codecov Report

Merging #92 (8c614c4) into main (e640666) will decrease coverage by 7.43%.
The diff coverage is 61.96%.

@@            Coverage Diff             @@
##             main      #92      +/-   ##
==========================================
- Coverage   87.58%   80.14%   -7.44%     
==========================================
  Files          18       20       +2     
  Lines         572      806     +234     
==========================================
+ Hits          501      646     +145     
- Misses         52      129      +77     
- Partials       19       31      +12     

Flag	Coverage Δ
Linux	78.90% <57.69%> (-8.68%)	⬇️
Windows	79.40% <60.68%> (-7.66%)	⬇️
macOS	78.16% <56.41%> (-8.90%)	⬇️

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Impacted Files	Coverage Δ
...n/github.com/lib/pq/splunkpq/internal/connector.go	56.78% <56.78%> (ø)
instrumentation/github.com/lib/pq/splunkpq/sql.go	91.42% <91.42%> (ø)

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