Draft: flutter: Add layer

This revision belong to honister branch and it has been checked on onrio kirkstone base using downstream project meta-oniro-blueprint-flutter.

Relate-to: https://gitlab.eclipse.org/groups/eclipse-wg/oniro-wg/proposal-incubation-stage-oniro/-/wikis/UI Origin: https://booting.oniroproject.org/distro/oniro/-/merge_requests/541 Forwarded: https://gitlab.eclipse.org/eclipse/oniro-core/oniro/-/merge_requests?scope=all&state=opened&author_username=pcoval Signed-off-by: Philippe Coval philippe.coval@huawei.com