Add instrumentation for average number of approvals required

What does this MR do and why?

This merge request adds two new metrics for counting the average number of deployment approvals required for protected environments that require an approval. There are two ways a protected environment could have approvals required, and this ensures both of them are counted.

Resolves #361811 (closed).

How to set up and validate locally

1. Navigate to Admin Area > Settings > Metrics and profiling.
2. Under Usage Statistics, check the preview payload of service ping to see the new metrics.

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.