refactor the ROSA Scheduled Run workflow's prometheus metrics action files

[kami619]

Description

Refactor the ROSA Scheduled Run workflow's Prometheus metrics action files.

As part of the #914 we updated the ROSA scheduled run's ability to get metrics from both clusters. However, the change increased the friction from the action files in the form of reduced re-usability of code. This ticket is to look at that opportunity to refactor the below aspects.

• Update the way we are retrieving the THANOS_HOST and OC_TOKEN per cluster and may be set in the benchmark workflow itself.
• Reduce the amount of bash script code used in the individual steps to compute the metrics.

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Motivation

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Details

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