Create test runtime for CI that inherits FD.o
Context
KDE is built with flatpak-builder instead of Buildstream and we already broke them once. We should have a test in CI that ensures inherited runtimes built that way work.
Description
We need a runtime that inherits FD.o built through CI. We should probably also have a test app that gets built against that runtime and in turn run.
Acceptance Criteria
CI prevents us from breaking child runtimes this easily.