[ibm-mq-metrics] Report queue manager uptime

[atoulme]

Component(s)

ibm-mq-metrics

Is your feature request related to a problem? Please describe.

The IBM MQ metrics integration reports a heartbeat metric. This metric returns 1 when the queue manager is up.
This metric could be more useful if it reported the cumulative number of seconds the queue manager is up, so we can catch any restarts.

Describe the solution you'd like

Adopt a new metric to report uptime of the queue manager.

Optionally, can be a followup issue: deprecate and remove the heartbeat metric.

Describe alternatives you've considered

No response

Additional context

No response

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