Change the Shard Split State Document to use a vector<tenant_id> instead of vector<string>. This should contain the changes for the shard_split_donor_service, shard_split_donor_op_observer. There might be some conflicts with the tenant_migration_access_blocker_registry which should be addressed in a different ticket, in the meantime we can have a temporary conversion from tenant_id to StringData. We should also make changes to all the unit tests and jstests if necessary (we do not seem to access the tenantIds from the state doc in our jstests).