Summary:
The `Statistics` objects are meant to be shared across translation
units, but this was prevented by declaring them static. We need to
ensure they are defined once in the program. The effect is now
`StressTest::PrintStatistics()` can actually print statistics since it
now sees non-null values when `--statistics=1`.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9260
Reviewed By: zhichao-cao
Differential Revision: D32910162
Pulled By: ajkr
fbshipit-source-id: c926d6f556177987bee5fa3cbc87597803b230ee
