refactor: use SplitButton from Catalyst instead of ConrifmButton

[kieckhafer]

Resolves #5421
Impact: minor
Type: refactor

Issue

At the time of original development, SplitButton was not yet available, therefore not used in places it should have been.

Solution

Update the UI to use SplitButton where needed, since it's now available in Catalyst. Also updated this component from a Class to a function component, and updated the mutation to use @apollo/react-hooks.

Breaking changes

None

Testing

1. Create an Order
2. See that the SplitButton component is now used in the Fulfillment Group section of the Orders Admin
3. See that the SplitButton works by changing shipment status as it should

[kieckhafer]

@reactioncommerce/design I'd like to show you how this works in action. It's a strange workflow, having to select something from the dropdown, and then also click the button. I feel like maybe the original way, where a dialog opens, is better.

[kieckhafer]

@machikoyasuda @mikemurray This is updated to use the new ActionMenu, which is available in Catalyst 1.8.

There is another PR that is updating Catalyst inside of reaction to 1.7.3, so my PR will bump it even further. We should probably just update the other PR to use 1.8.0 as well.

#5473

[willopez]

left a question in one of the files.

[willopez]

LGTM