Summary:
DBImpl::DumpStats is supposed to do this:
Dump DB stats to LOG
For each CF, dump CFStatsNoFileHistogram to LOG
For each CF, dump CFFileHistogram to LOG

Instead, due to a longstanding bug from 2017 (https://github.com/facebook/rocksdb/issues/2126), it would dump
CFStats, which includes both CFStatsNoFileHistogram and CFFileHistogram,
in both loops, resulting in near-duplicate output.

This fixes the bug.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8380

Test Plan: Manual inspection of LOG after db_bench

Reviewed By: jay-zhuang

Differential Revision: D29017535

Pulled By: pdillinger

fbshipit-source-id: 3010604c4a629a80347f129cd746ce9b0d0cbda6