chore: revert changing histogram to gauge

[grobinson-grafana]

What this PR does / why we need it:

This pull request reverts #16864. It has a number of problems such as the gauge still being omitted when the phase changes. I would like to revert it and then explore it further before keeping it as a gauge.

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• Documentation added
• Tests updated
• Title matches the required conventional commits format, see here
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