OSD: Sharded Op worker queue implementation for handling OSD ops

OSD: Sharded Op worker queue implementation for handling OSD ops
This is the implementation for the client of the
sharded thread pool/sharded workQ. Removed the op_wq class and now OSD
ops are going through sharded workqueue model which is used by the
sharded threadpool. Derived ShardedOpWQ implementation has a data structure
called ShardData which has it's own lock/cond and storage. ShardedOpWQ
holds a vector of that and the size of the vector is a config option.
During enqueue operation on the queue, the ops are sharded across these
ShardData based on pg hash % number of shards.
Similarly, in the _process function the sharded thread pool threads are
divided across ShardData based on thread index % number of shards

Signed-off-by: Somnath Roy <somnath.roy@sandisk.com>