main/postmarketos-ondev: upgrade to 0.2.0

Many new screens added, see this commit message for an overview.

Photos:

• welcome
• fde-optional
• lockscreen-pin (missing spaces noted and fixed here)
• ssh-credentials

There are two annoying known bugs which are not fixed in this release, be aware (https://gitlab.com/postmarketOS/postmarketos-ondev/-/issues/18, https://gitlab.com/postmarketOS/postmarketos-ondev/-/issues/15). But since postmarketos-ondev is still brand new and so many other things have been improved. It's time to make a new release.

This needs the pmbootstrap changes from MR pmbootstrap!1953 (merged) (both should be merged at the same time).

I'm also looking for UX feedback in the postmarketos-ondev issues.