Summary:
* Clarify that RocksDB is not exception safe on many of our callback
and extension interfaces
* Clarify FSRandomAccessFile::MultiRead implementations must accept
non-sorted inputs (see https://github.com/facebook/rocksdb/issues/8953)
* Clarify ConcurrentTaskLimiter and SstFileManager are not (currently)
extensible interfaces
* Mark WriteBufferManager as `final`, so it is then clearly not a
callback interface, even though it smells like one
* Clarify TablePropertiesCollector Status returns are mostly ignored
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9080
Test Plan: comments only (except WriteBufferManager final)
Reviewed By: ajkr
Differential Revision: D31968782
Pulled By: pdillinger
fbshipit-source-id: 11b648ce3ce3c5e5bdc02d2eafc7ea4b864bd1d2