Changes summary:
* make `cql3::result_set` movable-only
* change signature of `cql3::result::result_set` to return by cref
* adjust available call sites to the aforementioned method to accept cref
Motivation behind this change is elimination of dangerous API,
which can easily set a trap for developers who don't expect that
result_set would be returned by value.
There is no point in copying the `result_set` around, so make
`cql3::result::result_set` to cache `result_set` internally in a
`unique_ptr` member variable and return a const reference so to
minimize unnecessary copies here and there.
Tests: unit(debug)
Signed-off-by: Pavel Solodovnikov <pa.solodovnikov@scylladb.com>
Message-Id: <20191220115100.21528-1-pa.solodovnikov@scylladb.com>
5a15bed569