metric: migrate all histograms to use prometheus-backed version#1

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aadityasondhi wants to merge 2 commits intoaadityas/histogram-updatesfrom aadityas/histogram-upgrade-v2

+614-531

Commits on Aug 19, 2022

metric: export quantiles from prometheus-based histogram
aadityasondhi
committed

Commits on Aug 23, 2022

metric: migrate all histograms to use prometheus-backed version
aadityasondhi
committed