Add support for Micrometer Observation

[marcingrzejszczak]

Micrometer Observation is coming as part of the Micrometer 1.10 release and Micrometer Tracing is a new project. The idea of Micrometer Observation is that you instrument code once but you get multiple benefits out of it - e.g. you can get tracing, metrics, logging or whatever you see fit).

Since this project already supports Micrometer I was curious if there's interest in adding Micrometer Observation support so that except for metrics, spans could be created and tracing context propagation could happen too.

If there's such interest we could provide a PR to add support for that.

[acogoluegnes]

Fixed in #1017.