[PP-1] Replace the "Change field type" button with one that goes to the previous step

I think we should postpone this on 📌 [PP-1] Move label and machine name fields to the field config edit form Active because this would be quite tricky before it. At least after that, the first two steps control the type, and the last step controls everything else. I guess it's reasonable that if user changes the field type, that they lose any changes they've made on the last step. This is just my guess that would probably be worth confirming by usability tests.