Handling StatusNotFound in IBMMQ scaler

[rickbrouwer]

• Restructured response validation using switch statement for different HTTP status codes
• Renamed maxDepth to maxDepths for naming consistency with other depth calculation functions
• Added calculateDepth helper function
• Improved error handling in IBM MQ scaler:

If you configure something wrong, for example a small typo in the host param, an error will occur like:

error inspecting IBM MQ queue depth: failed to parse response from REST call for queue MY_QUEUE.LQ

You can easily overlook this and not know exactly what the error is.
To solve this I add a http.StatusNotFound that reads the message and presents it. This gives you a clearer message, like:

error inspecting IBM MQ queue depth: MQWB0009E: Could not query the queue manager 'MQMGRR'.

Checklist

• I have verified that my change is according to the deprecations & breaking changes policy
• Tests have been added
• Changelog has been updated and is aligned with our changelog requirements
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