Auto-configure JvmCpuMeterConventions bean on ProcessorMetrics

[mhalbritter]

Currently we're using

@Bean
@ConditionalOnMissingBean
ProcessorMetrics processorMetrics() {
  return new ProcessorMetrics();
}

The constructor can also take a JvmCpuMeterConventions, which I think we should auto-configure if a JvmCpuMeterConventions bean is around.

The same could be done for:

• JvmMemoryMetrics with JvmMemoryMeterConventions
• JvmThreadMetrics with JvmThreadMeterConventions
• ClassLoaderMetrics with JvmClassLoadingMeterConventions