log: add a helper for stdout logging during verbose test runs

[adamdecaf]

Often it's helpful to 'go test ./... -v' and get more data. This
is a handy helper method to switch between stdout and discard logging.

[codecov-commenter]

Codecov Report

Merging #231 (e3d3ab8) into master (08d3991) will increase coverage by 0.58%.
The diff coverage is 0.00%.

❗ Current head e3d3ab8 differs from pull request most recent head e29e978. Consider uploading reports for the commit e29e978 to get more accurate results

@@            Coverage Diff             @@
##           master     #231      +/-   ##
==========================================
+ Coverage   77.68%   78.27%   +0.58%     
==========================================
  Files          29       28       -1     
  Lines         932      925       -7     
==========================================
  Hits          724      724              
+ Misses        162      155       -7     
  Partials       46       46              

Impacted Files	Coverage Δ
log/logger_impl.go	90.00% <0.00%> (-4.74%)	⬇️
database/sqlite_nocgo.go

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