This detaches *like_operator*, *group_by*, *functions*
and *large* cases into own files. The split is not
uniform -- the resulting 4 tests run less that 3 minutes
each, what's left in the origin runs ~11 minutes. But
since the goal was to get out of 14 minutes threshold
and this file contains 126 cases (the champion) so I
just did "wildcard" selection that worked.
It also required moving require_rows() helpers into a
local header.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
