Remove clone for types which do not involve copying

[sashacmc]

Removes:

• z_subscriber_clone
• z_publisher_clone
• z_queryable_clone
• z_session_clone

Closes: #639

[DenisBiryukov91]

There is a deep copy function _z_keyexpr_copy that can be used for proper z_keyexpr clone (zenoh-c has a keyexpr clone).
User might also likely need a clone for reply_err aka value (zenoh-c has a reply err clone).
I would also remove z_session_clone since it is not a side-effects free operation (zenoh-c does not have a session clone).

[sashacmc]

We also need to add a z_config_clone implementation, but it will be done in separate PR