Summary:
Update the signature of Poll and ReadAsync APIs in filesystem.
Instead of unique_ptr, void** will be passed as io_handle and the delete function.
io_handle and delete function should be provided by underlying
FileSystem and its lifetime will be maintained by RocksDB. io_handle
will be deleted by RocksDB once callback is made to update the results or Poll is
called to get the results.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9623
Test Plan: Add a new unit test.
Reviewed By: anand1976
Differential Revision: D34403529
Pulled By: akankshamahajan15
fbshipit-source-id: ea185a5f4c7bec334631e4f781ea7ba4135645f0
d74468e348