uts: add type for early boot properties
In early start and current code we build properties as <name, byte stream> pair and to create the DDI properties in uts/i86pc/os/ddi_impl.c:get_boot_properties() by identifying them by name and attaching the type (as is).
The core of the change is to create typed BOP properties. The most visible result is that we simplify the DDI property setup. If or in what extent we should implement the value validation - I would leave that for future updates. For testing - so far I have not seen any unexpected behavior regarding to properties.