Add agl-ivi-demo-platform-flutter-simple

Add agl-ivi-demo-platform-flutter-simple

Add agl-ivi-demo-platform-flutter-simple image recipe that is
equivalent to the previous agl-ivi-demo-platform-flutter before
switching to using flutter-ics-homescreen.  This allows testing
with the previous flutter-homescreen, flutter-hvac, and
flutter-dashboard applications.  Per the 11/23 developer call,
this is desirable for Quillback since it will be a LTS release.

Bug-AGL: SPEC-4982

Change-Id: If4ae33ef25e986fe32802a9e6ca299f941e5ef2f
Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl-demo/+/29470
ci-image-boot-test: Jenkins Job builder account
Tested-by: Jenkins Job builder account
ci-image-build: Jenkins Job builder account
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>