Port MovingAverage as-is from legacy to v2

[jmao-denver]

Skipped creating a unit test for it but tested with the example in the docs.

from deephaven.experimental.ema import ByEmaSimple
from deephaven import time_table
import random

def random_char():
    return random.choice(['A', 'B', 'C', 'D', 'E', 'F'])

ema1sec = ByEmaSimple('BD_SKIP','BD_SKIP','TIME',10,'SECONDS', type='LEVEL')

result = time_table('00:00:01').update(formulas=["Sym = (String)random_char()", "Numbers = (int)random.randint(0, 100)"])

ema_data = result.view(formulas=["EMA_data = ema1sec.update(Timestamp, Numbers)"]).last_by()
ema_data_grouped = result.view(formulas=["Sym", "EMA_data = ema1sec.update(Timestamp, Numbers, Sym)"]).last_by(by=["Sym"]).sort(order_by=["Sym"])

Fixes #2386

[chipkent]

Suggested change

	"""Constructor for an engine aware Exponential Moving Average (EMA) which performs a `groupBy` ema calculation without
	"""Constructor for an engine aware Exponential Moving Average (EMA) which performs a `group_by` ema calculation without

[jmao-denver]

I think groupBy is OK because we are talking about the operation on the server.