Document and provide a way to disable global state modification by Collector

[mx-psi]

Is your feature request related to a problem? Please describe.

On initialization, the Collector modifies global state from external dependencies in a number of ways; for example (probably not an exhaustive list!):

• Modify the global gRPC logger

  opentelemetry-collector/service/internal/telemetrylogs/logger.go

  Line 76 in 52f8669

  grpclog.SetLoggerV2(logger)

• Modify the global meter provider when using the OTel metrics feature flag

  opentelemetry-collector/service/telemetry.go

  Line 213 in f980c9e

  global.SetMeterProvider(pe.MeterProvider())

• Modify the global trace provider

  opentelemetry-collector/service/collector.go

  Line 215 in 52f8669

  otel.SetTracerProvider(col.tracerProvider)

All of these provide useful features, but it makes it difficult to use the Collector as a library: in the grpc logger example in particular, it can lead to data races since the logger access is not atomic, in the global providers it may interact in unexpected ways with other parts of a codebase.

Describe the solution you'd like

The Collector's documentation will explicitly state any global state modifications of externally accessible structs. It also provides an option to disable these modifications. In the cases listed above, something like #4970 would work, since it could be the telemetry provider's responsibility to modify global telemetry state.

[dmitryax]

@mx-psi will you be able to work on this one?

[mx-psi]

Sure :)

[bogdandrutu]

Removed the TraceProvider global #5138, working on the MeterProvider next.

[mx-psi]

👍 will focus just on the gRPC logger then

[bogdandrutu]

#5146 fixed the MeterProvider.

[mx-psi]

#5272 fixed the grpc logger temporarily. I am going to close this for now and we should reopen if the temporary fix is reverted