Remove most of the NetworkStack dependencies on frameworks/base.

Most of these files are being moved to the networkstack-client
library in packages/modules/NetworkStack, with the exception of
DhcpResultsCompatUtil which is unused and is being deleted.

Test: m
Bug: 151052811
Original-Change: https://android-review.googlesource.com/1734913
Merged-In: I72ec43987faf9138cd68dc47c6bf2abe8c67aa38
Change-Id: I72ec43987faf9138cd68dc47c6bf2abe8c67aa38