Summary:
In making `SstFileMetaData` inherit from `FileStorageInfo`, I
overlooked setting some `FileStorageInfo` fields when then default
`SstFileMetaData()` ctor is used. This affected `GetLiveFilesMetaData()`.
Also removed some buggy `static_cast<size_t>`
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9769
Test Plan: Updated tests
Reviewed By: jay-zhuang
Differential Revision: D35220383
Pulled By: pdillinger
fbshipit-source-id: 05b4ee468258dbd3699517e1124838bf405fe7f8
e6bca1a54e