prometheus: Expose 3 activity metrics #3194

Job	Run time
build (ubuntu-latest, 3.8)	14s
Check Links	11s
check_release	16s
build (ubuntu-latest, 3.11)	14s
integration_check (ubuntu-latest, 3.8)	11s
build (windows-latest, 3.8)	10s
integration_check (ubuntu-latest, 3.9)	9s
integration_check_pypy	12s
build (windows-latest, 3.11)	10s
Make SDist	12s
integration_check (ubuntu-latest, 3.10)	15s
build (macos-latest, 3.8)	13s
build (macos-latest, 3.11)	12s
Test Docs	14s
integration_check (ubuntu-latest, 3.11)	13s
Test Examples	11s
build (windows-latest, 3.9)	9s
build (ubuntu-latest, pypy-3.8)	12s
Test Lint	8s
Test Minimum Versions	16s
build (macos-latest, 3.10)	14s
Test Prereleases	16s
build (ubuntu-latest, 3.12)	16s
Install from SDist and Test	1s
coverage	1s
tests_check	1s
	4m 51s

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