Resolve "Prometheus graphs occasionally have incorrect Y scale"

What does this MR do?

Ensures prometheus graph values are typecast as Numbers to prevent quirks with string comparison. This was causing issues in which graphs would have an incorrect Y-axis because when using d3.max to find the maximum value for the graph, a series like ["0", "9.5", "20.1"] would return "9.5" as the max value since it was compared as a string, not a number.

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

Screenshots (if relevant)





Does this MR meet the acceptance criteria?

What are the relevant issue numbers?

Closes #38789 (closed)

Edited by Mike Greiling

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