service: allow telemetry.Factory to be injected

[axw]

Description

• Change service.Config.Telemetry's type to component.Config, so the concrete type can be controlled by the factory.
• Add service.Config.Settings.TelemetryFactory, so callers (i.e. otelcol) can inject the factory.
• Add otelcol.Factories.Telemetry, so distributions can control the telemetry factory, and inject it into the service settings.
• Change the telemetry.Factory interface to create all the providers together. There's a few reasons for this:
  • The service always creates all of them
  • At least in the default implementation, they are tightly coupled in that they share an SDK object
  • It simplifies accessing the logger during creation of meter and tracer providers, e.g. to log that they are disabled
• Add a telemetry.Factory method for creating a pcommon.Resource. This is needed since the resource may be configured through service::telemetry, which is now opaque to the service code.
• Move the view configuration into service/telemetry. This is not ideal, and should rather be injected as options when creating the MeterProvider. This is not currently possible, as otelconf does not support it.

Link to tracking issue

Fixes #4970

Testing

Documentation