[Housekeeping] Remove isDestructive button input

[RasmusKjeldgaard]

• I have written a good issue

Describe the housekeeping request

isDestructive is an undocumented input on the button that should only used internally, but is publicly available on the button component.

It is used to mark a button destructive in the alert component.

It can be removed in favor of applying the destructive class on the specific button inside the alert-component markup.

Have you considered any alternatives?

Leave it in there, but it complicated the button rework in #2602 and #2684