GH-3643: Defer MeterRegistry bean dependency

[artembilan]

Fixes #3643

The ImportBeanDefinitionRegistrar register its bean definition in the early phase.
It causes a problem with Spring Boot when an explicit @EnableIntegrationManagement
is declared: the MeterRegistry is provided later on via auto-configuration
and MicrometerMetricsCaptor has no knowledge about MeterRegistry at the
ImportBeanDefinitionRegistrar phase.

• Reworks MicrometerMetricsCaptorRegistrar to the MicrometerMetricsCaptorConfiguration
  and use special conditional MicrometerMetricsCaptorImportSelector for that
  @EnableIntegrationManagement.
  This way a MicrometerMetricsCaptor @Bean consults ObjectProvider<MeterRegistry>
  on its creating time and returns null if no MeterRegistry beans at all.

[artembilan]

Note: this is some kind of breaking change and with provided workaround in the issue dictate us no back-port policy.
With that we also may reject the PR for current 5.5.x version and just defer it to the next major 6.0.
But still: we never advertise MicrometerMetricsCaptorRegistrar for end-user interaction.
Although another breaking change may be observed when MetricsCaptor bean and @EnableIntegrationManagement declared explicitly. Which is also not right way to have in the target project: or annotation or explicit beans.
Therefore my intention to have this fix on board for consistency with exiting annotation model in Spring Framework.