Add parceling for DhcpServingParams

Introduce a stable AIDL parcel class, DhcpServingParamsParcel, and
methods to convert to and from that class to DhcpServingParams.
This will be used to move DhcpServer to the NetworkStack app.

Test: atest FrameworksNetTests
Bug: b/112869080
Change-Id: I276b7affccb938059769c90a53f0f6beb26e6ede