Add "const" attributes to `assignment_testable::test_assignment`
and `term::raw::prepare` methods. These should have been marked as
"const" even before the change but for some reason were missing
these qualifiers.
Mark other supplementary methods with "const" attributes as
necessary.
Tests: unit(dev, debug)
Signed-off-by: Pavel Solodovnikov <pa.solodovnikov@scylladb.com>
Message-Id: <20200127213215.494000-1-pa.solodovnikov@scylladb.com>