fix: histogram could measure up to 10 seconds of consumption lag, needs exponential buckets

[grobinson-grafana]

What this PR does / why we need it:

This pull request fixes a bug where the histogram could not measure more than 10 seconds of lag, as DefBuckets stops at 10. We need to use ExponentialBuckets like the other consumption lag metrics.

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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