The logic is similar to how oe-core and poky handle their set of sample
configurations. The core difference is the fact that we only flag
currently (no automatic migrations yet) by providing a helpful build
error before parsing. In this way we can instruct an user to update
their bblayers.conf when the Oniro introduced new lateyers integrations.

The variables of interest here are ONIRO_LAYERS_CONF_VERSION and
ONIRO_REQUIRED_LAYERS_CONF_VERSION. Whenever the project's
bblayers.conf.sample changes, we need to bump both of these values.

Signed-off-by: Andrei Gherzan <andrei.gherzan@huawei.com>