fix(injector: builtin: sql): driver is not registered from non-instrumented sql calls

[eliottness]

gopkg.in/DataDog/dd-trace-go.v1/contrib/database/sql.Register actually does not call database/sql.Register under the hood so we have to do it ourselves

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 63.66%. Comparing base (a8237ee) to head (b54d49a).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #411      +/-   ##
==========================================
- Coverage   64.23%   63.66%   -0.57%     
==========================================
  Files         185      185              
  Lines       11087    11095       +8     
==========================================
- Hits         7122     7064      -58     
- Misses       3420     3507      +87     
+ Partials      545      524      -21     

Components	Coverage Δ
Generators	78.12% <ø> (ø)
Instruments	73.41% <ø> (ø)
Go Driver	80.16% <ø> (ø)
Toolexec Driver	74.00% <ø> (ø)
Aspects	74.10% <ø> (ø)
Injector	74.97% <ø> (ø)
Job Server	68.18% <ø> (-5.28%)	⬇️
Integration Test Suite	57.20% <100.00%> (+0.05%)	⬆️
Other	63.66% <100.00%> (-0.57%)	⬇️

Files with missing lines	Coverage Δ
_integration-tests/tests/sql/sql.go	100.00% <100.00%> (ø)

... and 2 files with indirect coverage changes

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