[Batch] Change batch step default for full_event to True

[tomerm-iguazio]

This PR update Batch step default to full_event=True.
It also updates all Batch steps tests to operate also with full events throughout.

ML-12099

[gtopper]

Looks good overall, in line with the decision as cited in https://iguazio.atlassian.net/browse/ML-12099?focusedCommentId=207050.

Please update the PR title to reflect the fact that support isn't removed, but rather deprecated, with the default value changed.

Please make sure this change gets a release note.

Would be good to add a test for the deprecation warning itself, e.g.:

def test_batch_warns_when_full_event_not_specified():
    with pytest.warns(FutureWarning, match="full_event"):
        Batch(4, 100)

While this is a concern we can defer, there are tests in storey and mlrun that would fail once Batch(full_event=False) is actually blocked. See test_to_dataframe_with_index and test_batch_by_user_key in storey, and test_batch in mlrun for examples.