Add a general method to check version validity of DeviceConfig property.

Considering boolean experimental flag is likely to cause misconfiguration,
particularly when NetworkStack module rolls back to previous version. It's
much safer to determine whether or not to enable one specific experimental
feature by comparing flag version with module version.

Test: atest NetworkStackTests

Change-Id: Ie0c9527eb87b75c998584f2b4439cc0e309e8b28