Data check actions: don't produce duplicate components

[angela97lin]

Currently, we could add multiple duplicate components from the same actions. We should try to prune duplicate components, if possible:

# current behavior. But this might cause errors, trying to drop 'some col' multiple times
actions = [DataCheckAction(DataCheckActionCode.DROP_COL, {"columns": ['some col']}),
                  DataCheckAction(DataCheckActionCode.DROP_COL, {"columns": ['some col']})]
_make_component_list_from_actions(actions) == [DropColumns(columns=['some col']),
                                                                    DropColumns(columns=['some col'])] 

# desired behavior
actions = [DataCheckAction(DataCheckActionCode.DROP_COL, {"columns": ['some col']}),
                  DataCheckAction(DataCheckActionCode.DROP_COL, {"columns": ['some col']})]
_make_component_list_from_actions(actions) == [DropColumns(columns=['some col'])] # only once

There's some support in the DataChecks class to not return duplicate actions, but if a user just used multiple DataCheck objects, we will still end up with duplicates in _make_component_list_from_actions

[dsherry]

@angela97lin is this blocked on #1730 ?

[angela97lin]

@dsherry Nope, not necessarily--just an additional enhancement / cleanup!

[dsherry]

This is not blocked on #1929 -- we can lump the dropped cols into one DropColumns component. However, it may make more sense if each action generates its own component, which we'd need to do #1929 for in order to put multiple DropColumns into a pipeline.