rust: device: Introduce PropertyGuard

rust: device: Introduce PropertyGuard

This abstraction is a way to force users to specify whether a property
is supposed to be required or not. This allows us to move error
logging of missing required properties into core, preventing a lot of
boilerplate in drivers.

It will be used by upcoming methods for reading device properties.

Tested-by: Dirk Behme <dirk.behme@de.bosch.com>
Signed-off-by: Remo Senekowitsch <remo@buenzli.dev>
Link: https://lore.kernel.org/r/20250611102908.212514-6-remo@buenzli.dev
[ Use prelude::* to avoid build failure; move PropertyGuard below Display
  impl of FwNode. - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>