store logger in context, move LogsMessagesTrait into API

[brettmc]

remove global/static LoggerHolder, and store logger in Context via Globals. LoggerHolder is deprecated, but a temporary BC hack should avoid immediate breakage.
Move LogsMessagesTrait into API, since there is a requirement (and some outstanding todo's) in the API layer to emit warnings in certain situations.

Closes #889

[codecov]

Codecov Report

Merging #891 (f5f2cf1) into main (7bfc121) will decrease coverage by 0.02%.
The diff coverage is 89.47%.

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #891      +/-   ##
============================================
- Coverage     81.59%   81.56%   -0.03%     
+ Complexity     2010     2008       -2     
============================================
  Files           264      264              
  Lines          5226     5230       +4     
============================================
+ Hits           4264     4266       +2     
- Misses          962      964       +2     

Flag	Coverage Δ
7.4	81.04% <89.47%> (-0.03%)	⬇️
8.0	81.55% <89.47%> (-0.03%)	⬇️
8.1	81.69% <89.47%> (-0.03%)	⬇️

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Impacted Files	Coverage Δ
src/Contrib/Grpc/GrpcTransportFactory.php	52.27% <ø> (ø)
src/Contrib/Jaeger/AgentExporter.php	100.00% <ø> (ø)
src/Contrib/Jaeger/HttpSender.php	100.00% <ø> (ø)
src/Contrib/Jaeger/JaegerTransport.php	86.66% <ø> (ø)
src/Contrib/Newrelic/Exporter.php	100.00% <ø> (ø)
src/Contrib/Otlp/MetricExporter.php	38.70% <ø> (ø)
src/Contrib/Otlp/SpanExporter.php	77.77% <ø> (ø)
src/Contrib/Otlp/SpanExporterFactory.php	100.00% <ø> (ø)
src/Contrib/Zipkin/Exporter.php	100.00% <ø> (ø)
src/Contrib/ZipkinToNewrelic/Exporter.php	85.00% <ø> (ø)
... and 15 more

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[Nevay]

I don't think we should make a PSR logger accessible via Globals, considering that the spec contains an experimental logging backend (also the reason why I dropped Globals::logger() from #822). IMO we should instead switch to using an otel Logger for our self-diagnostics once implemented.

[brettmc]

I don't think we should make a PSR logger accessible via Globals, considering that the spec contains an experimental logging backend (also the reason why I dropped Globals::logger() from #822). IMO we should instead switch to using an otel Logger for our self-diagnostics once implemented.

That makes sense, I'll close this one and do a simple migration from SDK to API.