Summary:
Adds changes to DBOptions (comparable to ColumnFamilyOptions) to allow some option values to be ignored on rehydration from the Options file.  This is necessary for some customizable classes that were not registered with the ObjectRegistry but are saved/restored from the Options file.

All tests pass.  Will run check_format_compatible.sh shortly.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/9045

Reviewed By: zhichao-cao

Differential Revision: D31761664

Pulled By: mrambacher

fbshipit-source-id: 300c2251639cce2b223481c3bb2a63877b1f3766