[geneva] Nullable annotations for MsgPackExporter folder

[CodeBlanch]

Changes

• Adds nullable annotations for the MsgPackExporter folder inside the GenevaExporter project
• Updates the folder structure & namespaces between TldExporter & MsgPackExporter to be more consistent

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)
• Unit tests added/updated

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69.57%. Comparing base (71655ce) to head (ae7a023).
Report is 443 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2092      +/-   ##
==========================================
- Coverage   73.91%   69.57%   -4.35%     
==========================================
  Files         267      330      +63     
  Lines        9615    12388    +2773     
==========================================
+ Hits         7107     8619    +1512     
- Misses       2508     3769    +1261     

Flag	Coverage Δ
unittests-Exporter.Geneva	53.15% <100.00%> (?)
unittests-Exporter.InfluxDB	95.88% <ø> (?)
unittests-Exporter.Instana	71.24% <ø> (?)
unittests-Exporter.OneCollector	94.19% <ø> (?)
unittests-Exporter.Stackdriver	75.73% <ø> (?)
unittests-Extensions	88.57% <ø> (?)
unittests-Extensions.AWS	83.41% <ø> (?)
unittests-Extensions.Enrichment	100.00% <ø> (?)
unittests-Instrumentation.AWS	84.78% <ø> (?)
unittests-Instrumentation.AWSLambda	88.92% <ø> (?)
unittests-Instrumentation.AspNet	76.73% <ø> (?)
unittests-Instrumentation.AspNetCore	85.27% <ø> (?)
unittests-Instrumentation.ConfluentKafka	14.12% <ø> (?)
unittests-Instrumentation.ElasticsearchClient	79.87% <ø> (?)
unittests-Instrumentation.EntityFrameworkCore	55.49% <ø> (?)
unittests-Instrumentation.EventCounters	76.36% <ø> (?)
unittests-Instrumentation.GrpcNetClient	79.61% <ø> (?)
unittests-Instrumentation.Hangfire	93.58% <ø> (?)
unittests-Instrumentation.Http	82.05% <ø> (?)
unittests-Instrumentation.Owin	85.97% <ø> (?)
unittests-Instrumentation.Process	100.00% <ø> (?)
unittests-Instrumentation.Quartz	78.94% <ø> (?)
unittests-Instrumentation.Runtime	100.00% <ø> (?)
unittests-Instrumentation.SqlClient	90.90% <ø> (?)
unittests-Instrumentation.StackExchangeRedis	67.02% <ø> (?)
unittests-Instrumentation.Wcf	48.91% <ø> (?)
unittests-PersistentStorage	65.78% <ø> (?)
unittests-Resources.AWS	77.93% <ø> (?)
unittests-Resources.Azure	82.35% <ø> (?)
unittests-Resources.Container	72.41% <ø> (?)
unittests-Resources.Gcp	72.54% <ø> (?)
unittests-Resources.Host	73.94% <ø> (?)
unittests-Resources.OperatingSystem	77.20% <ø> (?)
unittests-Resources.Process	100.00% <ø> (?)
unittests-Resources.ProcessRuntime	77.08% <ø> (?)
unittests-Sampler.AWS	87.74% <ø> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...OpenTelemetry.Exporter.Geneva/GenevaLogExporter.cs	56.41% <ø> (-21.09%)	⬇️
...enTelemetry.Exporter.Geneva/GenevaTraceExporter.cs	51.28% <ø> (-23.72%)	⬇️
...xporter.Geneva/Internal/ConnectionStringBuilder.cs	94.11% <100.00%> (+1.17%)	⬆️
.../Internal/MsgPackExporter/MessagePackSerializer.cs	90.20% <100.00%> (ø)
...Geneva/Internal/MsgPackExporter/MsgPackExporter.cs	93.93% <100.00%> (ø)
...eva/Internal/MsgPackExporter/MsgPackLogExporter.cs	93.05% <100.00%> (ø)
...a/Internal/MsgPackExporter/MsgPackTraceExporter.cs	93.57% <100.00%> (ø)
...ry.Exporter.Geneva/Internal/TableNameSerializer.cs	98.93% <ø> (ø)
...rter.Geneva/Internal/TldExporter/JsonSerializer.cs	36.71% <ø> (ø)
...xporter.Geneva/Internal/TldExporter/TldExporter.cs	0.00% <ø> (ø)
... and 7 more

... and 354 files with indirect coverage changes