Integrate Camunda metrics into Spring Boot Actuator registry

[ThorbenLindhauer]

This issue was imported from JIRA:

Field	Value
JIRA Link	CAM-14729
Reporter	@tmetzke
Has restricted visibility comments	true

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User Story (Required on creation):

• As a System Administrator, I want to see exposed engine metrics as part of all the metrics (for Camunda Spring Boot Starter or Camunda Run) accessible through the Spring Boot Actuator so that I can monitor the system.
• As an Operations Engineer, I can see the metrics my System Administrator exposed for me, to indicate the system's health.

Functional Requirements (Required before implementation):

• I can use the Micrometer metrics facades described in Actuator to monitor Camunda performance and usage metrics

Technical Requirements (Required before implementation):

• Add monitoring metrics to CamundaBpmActuatorConfiguration
• Fetch metrics from configured engine collector via API in a configurable interval (can be a different interval than the internal metrics DbReporter’s interval)
• Add collected metrics to Actuator’s Micrometer registry

Limitations of Scope (Optional):

Hints (optional):

• We already have a Camunda Actuator auto-configuration, defining health endpoints for the engine and the job executor

Links:

• depends on https://jira.camunda.com/browse/CAM-14727

### camunda-bpm-platform PR
- [ ] https://github.com/camunda/camunda-bpm-platform/pull/4519

### camunda-docs-manual PR