Changed how the telemetryInitializer is created

[cpheps]

Description:
Changed how the telemetryInitializer is created. Previously only a single instance of the telemetryInitializer was created for a process. The caused an issue if a Collector instance was shutdown and a new one was created the new instance would get the global instance that was shutdown as a result of the first Collector instance being shutdown.

The new logic ensures the feature gate is only registered once but a new telemetryInitializer instance is created per instance of the collector.

Link to tracking Issue:
Tangentially related to #5084.

In that issue the desired design is:

I think we are going to the direction to follow the language pattern which is after Shutdown you cannot call Run on the same instance, you have to create a new instance.

I believe this respects that design and fixes a bug where a new instance could not fully startup with the same expectations as the previous instance.

Testing:
Modified unit tests. Also, tested with our OPAMP enabled agent and server to verify that we can create a new instance of the collector with a changed config in a single process and have telemetry still be active. Previously it would not be.

[codecov]

Codecov Report

Base: 91.89% // Head: 91.90% // Increases project coverage by +0.00% 🎉

Coverage data is based on head (ce253e0) compared to base (b7ac70a).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6138   +/-   ##
=======================================
  Coverage   91.89%   91.90%           
=======================================
  Files         217      217           
  Lines       13319    13322    +3     
=======================================
+ Hits        12240    12243    +3     
  Misses        850      850           
  Partials      229      229           

Impacted Files	Coverage Δ
service/collector.go	78.90% <100.00%> (ø)
service/telemetry.go	90.06% <100.00%> (+0.20%)	⬆️

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[cpheps]

For CI failures
Looks like codecov got a 404 on upload and that the contrib tests are currently broken but being fixed.

[djaglowski]

Is there a particular PR that is supposed to fix the contrib tests? If so, will you link it here so we can track it?

[cpheps]

Is there a particular PR that is supposed to fix the contrib tests? If so, will you link it here so we can track it?

I believe it was this PR open-telemetry/opentelemetry-collector-contrib#14390. The contrib tests look like the fail due to a signalfx go mod error.

[djaglowski]

This LGTM.

[djaglowski]

@open-telemetry/collector-maintainers, anyone available to take a look at this one?