feat: add missing spacing utils from 1-7

What does this MR do?

The filesize different is negligible, the convenience of having all the margin/padding utils is significant.

Added 1-7 as 2rem is a sensible maximum to me, beyond that you should probably be either adding spacings of different elements, or considering an alternate means of spacing.

Doesn't this mean we are adding a bunch of util classes that we aren't using?

We already do! There are a few where only the mixin is used, but never the util class. The impact is between tiny and none.