"micrometer.observations.*" configuration properties should be "management.observations.*"

Introducing the `micrometer.observations.annotations.enabled` configuration property in that namespace was a mistake introduced in #39128 and we should move it to `management.observations.annotations.enabled`.

As part of this issue, we should try to support both and deprecate `micrometer.observations.annotations.enabled` in our metadata, for removal in a future Spring Boot version.