Add Parcelable implementation for ApfCapabilities

This is necessary to allow usage of ApfCapabilities as-is in AIDL,
instead of relying on ApfCapabilitiesParcelable, assuming that stable
AIDL starts allowing usage of @SystemApi classes. The Parcelable
implementation would be convenient for clients in any case.

Bug: 126477266
Test: atest FrameworksNetTests
Change-Id: Id2ef3cad261832a2918ccb6bb6bc154d99d75746