Create util function to return multiple DataChain instances, each for added, deleted and modified value of chain diff

[ilongin]

Now that we have DataChain.compare() implemented, we need another util function to return specific chain based on diff column.

Interface will be:

def compare(
    left: "DataChain",
    right: "DataChain",
    on: Union[str, Sequence[str]],
    right_on: Optional[Union[str, Sequence[str]]] = None,
    compare: Optional[Union[str, Sequence[str]]] = None,
    right_compare: Optional[Union[str, Sequence[str]]] = None,
    added: bool = True,
    deleted: bool = True,
    modified: bool = True,
    unchanged: bool = False,
) -> "DataChain":