[logs-branch] Support loading OtlpLogExporter envvars from IConfiguration

[CodeBlanch]

Relates to #3760

Changes

Applies the IConfiguration pattern to OtlpLogExporter paths.

TODOs

• Appropriate CHANGELOG.md updated for non-trivial changes

[codecov]

Codecov Report

Merging #3812 (095a8e9) into main-logs (aba8a69) will increase coverage by 0.01%.
The diff coverage is 100.00%.

❗ Current head 095a8e9 differs from pull request most recent head 1830453. Consider uploading reports for the commit 1830453 to get more accurate results

Additional details and impacted files

@@              Coverage Diff              @@
##           main-logs    #3812      +/-   ##
=============================================
+ Coverage      87.60%   87.62%   +0.01%     
=============================================
  Files            304      304              
  Lines          11476    11491      +15     
=============================================
+ Hits           10054    10069      +15     
  Misses          1422     1422              

Impacted Files	Coverage Δ
...ryProtocol.Logs/OtlpLogExporterHelperExtensions.cs	71.42% <100.00%> (+10.31%)	⬆️
...metryProtocol/OtlpTraceExporterHelperExtensions.cs	94.73% <100.00%> (ø)
...lder/ProviderBuilderServiceCollectionExtensions.cs	100.00% <100.00%> (ø)
...Telemetry/Logs/Builder/LoggerProviderBuilderSdk.cs	96.55% <100.00%> (ø)
....Exporter.OpenTelemetryProtocol/OtlpLogExporter.cs	66.66% <0.00%> (-8.34%)	⬇️
...emetry.Api/Internal/OpenTelemetryApiEventSource.cs	76.47% <0.00%> (-5.89%)	⬇️
...p/Implementation/HttpInstrumentationEventSource.cs	72.00% <0.00%> (-4.00%)	⬇️
...Telemetry/Internal/SelfDiagnosticsEventListener.cs	97.65% <0.00%> (+0.78%)	⬆️
src/OpenTelemetry/BatchExportProcessor.cs	84.11% <0.00%> (+1.86%)	⬆️
... and 1 more