Enhancement: RefreshScope should rebind MeterRegistry metrics

When using the spring cloud config server and changing a property value registered as Metric in a MeterRegistry, the value is not refreshed automatically.

As a first use case, suppose you want to change the value of a Hikari connections pool size:
from spring.datasource.hikari.maximumPoolSize=5 to spring.datasource.hikari.maximumPoolSize=10
(and adding spring.cloud.refresh.extra-refreshable=javax.sql.DataSource in my personal case),
the new created datasource won't appear as a new metric in the MeterRegistry who keeps the old one.
To circumvent this issue, I'm currently using a BeanPostProcessor
to remove the old datasource metrics and to rebind the new datasource to the registry.

/*
When changing a datasource value at runtime, the Prometheus Metrics registry does not pick up the changes automatically.
We have to remove the old datasource values and rebind the new datasource with the registry.
*/
public class DataSourceMetricsRefresher implements BeanPostProcessor {

  private final MeterRegistry registry;

  public DataSourceMetricsRefresher(MeterRegistry registry) {
    this.registry = registry;
  }

  @Override
  public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
    if (DataSource.class.isAssignableFrom(bean.getClass())) {
      HikariDataSource hikariDataSource = DataSourceUnwrapper.unwrap((DataSource) bean, HikariDataSource.class);
      List<Meter> meters = this.registry.getMeters();
      meters.stream().filter(meter -> meter.getId().getName().startsWith("hikaricp")).forEach(registry::remove);
      hikariDataSource.setMetricsTrackerFactory(new MicrometerMetricsTrackerFactory(this.registry));
    }
    return bean;
  }
}

As a second use case, suppose you want to enable/disable hibernate stats on the fly:
spring.jpa.properties.hibernate.generate_statistics=false
Here again, you have to do the same dance to rebind the HibernateMetrics to the registry.

This is not ideal and should be provided out of the box like it's done for logging in the LoggingRebinder.

Start by comparing the requested behavior with spring-cloud-context/src/main/java/org/springframework/cloud/logging/LoggingRebinder.java. Review the MeterRegistry usage in the issue, the referenced Micrometer HibernateMetrics entry point, and the BeanPostProcessor example. Done means refreshed datasource and Hibernate metrics are rebound automatically when configuration changes.