Buildstream should fail if it tries to build a project with a BST_FORMAT_VERSION not supported anymore

Summary

Similar to when we fail when the format_version of the project is greater than BST_FORMAT_VERSION, we should fail when the format_version of the project is below the lowes format supported by current version of buildstream

Steps to reproduce

Try to build https://gitlab.gnome.org/GNOME/gnome-build-meta/ with buildstream master

What is the current bug behavior?

buildstream fails with strange errors as It's trying to build a format it can not undertand anymore

What is the expected correct behavior?

buildstream should fail early with a descriptive message announcing it can not build a project with that specific format version