Create spacing classes based on tokens

[emilyjablonski]

In the process of uptaking seeds in core, we're having to add classes to module files just to add a single style like a bottom margin. These are the only kinds of styles we're experiencing this with. We should create classes that use both our semantic and global tokens for seeds spacings.

I don't think we generally want to follow this pattern to avoid where we can the inline messiness we experienced with Tailwind, but I think for now just spacings would be really helpful.

[emilyjablonski]

QA Notes
This doesn't need product QA!