DHC Python Breaking Time and RollingWAvg Change

[stanbrub]

A recent merge has changed how DH python references "now" for current time. Also, rolling_wavg_tick/time has changed the weight_col name to wcol.

• JoinTablesFromParquetAndStreamTest: Removing the import altogether should just use the java version
• DateTimeFormulaTest: Looks like the Java version of 'now' was already being used. Check it anyway
• In the event the Python version really is needed, do the below
• Update the rolling_wavg_tick and time benchmarks (Get rid of the weight_col param altogether?)

Was:

from deephaven.time import now
print('Time', now())

Change to:

from deephaven.time import dh_now
print('Time', dh_now())