Add tests for nomatch=NA in non-equi-join suite

[jangorecki]

Add tests for nomatch=NA in non-equi-join suite (tests 1640-ish)... tested, but takes quite some time... so commented for now

@jangorecki this set of tests could be added to the GitLab suite?

Is the TODO covered by the commented tests?

# TODO: add tests for nomatch=NA..
# tested, but takes quite some time.. so commenting for now
# nqjoin_test(x, y, 3L,1643.0)
# nqjoin_test(dt1,dt2,3L,1652.0)

# nqjoin_test(  x,dt2,1L,1644.0) # without NA only in x
# nqjoin_test(  x,dt2,2L,1645.0)
# nqjoin_test(  x,dt2,3L,1646.0)
# nqjoin_test(dt1,  y,1L,1647.0) # without NA only in i
# nqjoin_test(dt1,  y,2L,1648.0)
# nqjoin_test(dt1,  y,3L,1649.0)

Originally posted by @MichaelChirico in #2572 (comment)

[jangorecki]

best would be to simplify those tests so they can run faster.