Ability to customize the default ObservationEnvironmentRepositoryObservationConvention

Is your feature request related to a problem? Please describe.
Current implementation doesn't allow to customize the default ObservationEnvironmentRepositoryObservationConvention implementation. The default implementation adds to the lowCardinalityTags the application. This can be a problem when we have many applications, like our use case. This is exploding the cardinality for this metric when we expose this metric to prometheus and this is a known performance issue.

Describe the solution you'd like
I would like to be able to change the tags that are exported in metrics.

Describe alternatives you've considered
I tried to use an ObservationFilter as described in micrometer docs, but since it is a post-processing component it didn't take effect.

Start with spring-cloud-config-server/src/main/java/org/springframework/cloud/config/server/environment/ObservationEnvironmentRepositoryObservationConvention.java, especially the lowCardinalityTags handling linked in the issue. Review how the convention is selected and how the Micrometer observation customization described in the issue differs from post-processing; done means applications can change the exported tags without the default application tag causing excessive cardinality.