feat!: switch metric types to Gauges

[breed808]

Description

Particularly since 61153ae, the exporter has been observing requests over a time period rather than request totals. That is, metric values are no longer increasing monotonically.

Resolves #182

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Code refactoring
• Other (please describe):

Testing

• I have run make pr-tests and all tests pass
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

Code Quality

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation

Additional Notes

I should note this change is untested at the time of writing. I'm planning to run this in our environment sometime this week.

[haad]

Have you been able to test it ?

[asiyani]

Hi @haad sorry for the ping,
wondering if we can review this PR please.
This is a very important change, because as mentioned in the linked issue exporter is producing wrong metrics at the moment for all the counter metrics.
fwiw I think changes in this PR is correct and if there is any issue we should fix forward?
Thank you.

[breed808]

Apologies, I haven't been able to test this yet, and may not for a few weeks yet.

[haad]

Sure I'm happy to merge it once we get it tested by someone else this can also lead to breakage to other users dashboards.