Add feature gate to disable log teeing when telemetry provider is set

[ChrsMark]

Description

This PR adds a feature gate for disabling the console logging when a telemetry provider is configured for the Collector.

Link to tracking issue

Fixes #13019

Testing

Manual testing notes

1. Start a "back-end" Collector:

docker run \
  -p 127.0.0.1:4318:4318 \
  otel/opentelemetry-collector-contrib:0.128.0 \
  2>&1 | tee collector-output.txt

2. Using the following configuration, start a Collector with the featureGate enabled:
   config.yaml:

receivers:
  otlp:
    protocols:
      grpc:
        endpoint: 0.0.0.0:4317

exporters:
  debug:
    verbosity: normal

service:
  telemetry:
    logs:
      processors:
        - batch:
            exporter:
              otlp:
                protocol: http/protobuf
                endpoint: http://0.0.0.0:4318

  pipelines:
    metrics:
      receivers: [otlp]
      exporters: [debug]

./bin/otelcorecol_darwin_arm64 --config ~/otelcol/corecol/config.yaml --feature-gates=+telemetry.disableConsoleLoggingWhenProviderEnabled

3. Ensure that the back-end Collector receives the logs and that the monitored Collector does not log to the console

Documentation

Probably https://opentelemetry.io/docs/collector/internal-telemetry/ could mention the feature gate.

[codecov]

Codecov Report

Attention: Patch coverage is 81.81818% with 2 lines in your changes missing coverage. Please review.

Project coverage is 91.51%. Comparing base (8d71881) to head (51d1eaa).

Files with missing lines	Patch %	Lines
service/telemetry/logger.go	81.81%	1 Missing and 1 partial ⚠️

❌ Your patch check has failed because the patch coverage (81.81%) is below the target coverage (95.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #13209      +/-   ##
==========================================
- Coverage   91.51%   91.51%   -0.01%     
==========================================
  Files         522      522              
  Lines       28988    28998      +10     
==========================================
+ Hits        26529    26537       +8     
- Misses       1939     1940       +1     
- Partials      520      521       +1     

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