cql3: expression: don't copy expression in has_supporting_index()
cql3: expression: don't copy expression in has_supporting_index()

std::bind() copies the bound parameters for safekeeping. Here this
includes expr, which can be quite heavyweight. Use std::ref() to
prevent copying. This is safe since the bound expression is executed
and discarded before has_supporting_index() returns.

Closes #8791

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla