Fix H2OFrame.isin

[tomasfryda]

This is similar to what was done in R's %in% in #15929

The goal is to enable subsetting via frame[(frame[column].isin(values)), :] as it was before the AstMatch behavior changed.

Test:

import os
import sys
sys.path.insert(1, os.path.join("..", "..", ".."))

import h2o
from tests import pyunit_utils


def test_isin_issue():
    frame = h2o.upload_file(pyunit_utils.locate("smalldata/titanic/titanic_expanded.csv"))
    column = "cabin"
    levels = frame[column].levels()[0][:-10]
    assert len(levels) > 10
    print(frame[column].isin(levels).unique())
    # expecting a binary vector as in pandas
    assert frame[column].isin(levels).unique().nrows == 2
    assert frame.as_data_frame(use_pandas=True)[column].isin(levels).nunique() == 2


pyunit_utils.run_tests([test_isin_issue])