qa/tasks: Add a task which performs an offline check of the consistency of parity shards

Add a Python script which can be used to scan a Ceph cluster, find any erasure coded data objects and
check them for consistency. This is achieved by reading the data shards for a given object, running the data shards
through the existing EC tool and verifying the output matches the parity shards stored on the OSDs.

This commit adds a new teuthology task but does not add it to any YAMLs currently, this work will be
expanded on in future commits.

Signed-off-by: Connor Fawcett <[email protected]>
Fixes: https://tracker.ceph.com/issues/71412

Author: Connor Fawcett