remove MetricsLevel from TelemetrySettings

[codeboten]

A discussion on 4-Sept-2024 lead to the agreement that the struct field MetricsLevel will be removed from TelemetrySettings. This field is there to allow component authors to check a level before deciding whether to incur the cost of calculating an expensive operation.

The alternative for component authors will be to check whether an instrument is enabled or not prior to calculating the metric. This is dependent on the PR in otel go to implement this and on the spec to stabilize this feature.

The decision was that if the change would take too long to implement upstream, then we would remove this field and move any component to configure their own metric level instead. This will allow the unblocking of the component module stabilization work.

[mx-psi]

@bogdandrutu Are you going to submit any changes to the spec related to this? (Maybe related to open-telemetry/opentelemetry-specification/issues/4200?)

[mx-psi]

Given that stabilization of Enabled is not on September's release (see open-telemetry/opentelemetry-specification/pull/4204), I think we should go with the alternative plan, since mid-October would delay us significantly