Change the netId to nethandle mapping.

Being able to update this handle is necessary to ensure that
system-only OTAs do not break vendor code that relies on
nethandles.

Bug: 63052780
Test: walleye builds, boots, networking works
Test: MultinetworkApiTest CTS tests passes
Change-Id: I049a4ad2610ca68b8f56377b63be7e5e8ce76039