Migrate magnolia-blossom-sample-module to UI 6 framework

The current magnolia-blossom-sample-module is based on UI 5 framework. We need to migrate the module to UI 6 framework and move the old code to compatibility module.

EDIT: From the discussion below, we don't need to create a compatibility module. As there are already examples of working UI 6 definitions, migrating the rest of the sample should be trivial.