Debug Logging for sdk/trace

[MadVikingGod]

This addresses the lack of configuration visibility of our sdk.

Closes #2499

This does not address all exporters, just stdout. Aditional exporters can be addressed after we establish a working pattern.

[jmacd]

Looking forward to OTLP exporters having MarshalLog methods 🚀

[MadVikingGod]

To help people see how this change would affect things you can run the NamedTracer example and see the output:

/workspaces/opentelemetry-go/example/namedtracer $ go run . > /dev/null
2022/01/10 19:24:10 internal_logging.go:48: "level"=1 "msg"="TracerProvider created" "config"={"SpanProcessors":[{"Type":"BatchSpanProcessor","SpanExporter":{"Type":"stdout","WithTimestamps":true},"Config":{"MaxQueueSize":2048,"BatchTimeout":"5s","ExportTimeout":"30s","MaxExportBatchSize":512,"BlockOnQueueFull":false}}],"SamplerType":"trace.alwaysOnSampler","IDGeneratorType":"*trace.randomIDGenerator","SpanLimits":{"AttributeCountLimit":128,"EventCountLimit":128,"LinkCountLimit":128,"AttributePerEventCountLimit":128,"AttributePerLinkCountLimit":128},"Resource":{"Attributes":{"service.name":"unknown_service:namedtracer","telemetry.sdk.language":"go","telemetry.sdk.name":"opentelemetry","telemetry.sdk.version":"1.3.0"},"SchemaURL":"https://opentelemetry.io/schemas/v1.7.0"}}
2022/01/10 19:24:10 internal_logging.go:48: "level"=1 "msg"="Tracer created" "name"="example/namedtracer/main" "version"="" "schemaURL"=""
2022/01/10 19:24:10 internal_logging.go:48: "level"=1 "msg"="Tracer created" "name"="example/namedtracer/foo" "version"="" "schemaURL"=""
2022/01/10 19:24:10 internal_logging.go:62: "level"=5 "msg"="exporting spans" "count"=2 "dropped"=0

I would also like to add the formating of these logs in entirely controlled by the logger, so if we were to use for example a json logger we would have a different output.

[codecov]

Codecov Report

Merging #2500 (e47714b) into main (c37f485) will decrease coverage by 0.3%.
The diff coverage is 6.8%.

@@           Coverage Diff           @@
##            main   #2500     +/-   ##
=======================================
- Coverage   76.3%   76.0%   -0.4%     
=======================================
  Files        174     174             
  Lines      12027   12084     +57     
=======================================
+ Hits        9182    9188      +6     
- Misses      2600    2653     +53     
+ Partials     245     243      -2     

Impacted Files	Coverage Δ
attribute/set.go	61.8% <0.0%> (-1.8%)	⬇️
exporters/stdout/stdouttrace/trace.go	66.1% <0.0%> (-10.4%)	⬇️
sdk/resource/resource.go	77.8% <0.0%> (-4.8%)	⬇️
sdk/trace/simple_span_processor.go	74.5% <0.0%> (-12.7%)	⬇️
sdk/trace/batch_span_processor.go	79.4% <9.0%> (-6.1%)	⬇️
sdk/trace/provider.go	81.8% <17.6%> (-6.7%)	⬇️
sdk/metric/sdk.go	81.5% <0.0%> (+1.4%)	⬆️
sdk/metric/refcount_mapped.go	100.0% <0.0%> (+20.0%)	⬆️