Summary:
For better clarity, encouraging more options explicitly specified using fields rather than positionally via constructor parameter lists. Simplifies code maintenance as new fields are added. Deprecate some cases of the confusing pattern of NewWhatever() functions returning shared_ptr.

Net reduction of about 70 source code lines (including comments).

Pull Request resolved: https://github.com/facebook/rocksdb/pull/11386

Test Plan: existing tests

Reviewed By: ajkr

Differential Revision: D45059075

Pulled By: pdillinger

fbshipit-source-id: d53fa09b268024f9c55254bb973b6c69feebf41a