[2.0.7] Move SourceFormatter to ui_patterns_field

Chrsitian, I have tested the chnage, it works. But I just did a naive copy of the file from one module to the other (with some properties coming from the parent class), so feel free to challenge it.

Now that this issue is closed, please review the contribution record.

As a contributor, attribute any organization helped you, or if you volunteered your own time.

Maintainers, please credit people who helped resolve this issue.