Add SELinux configuration for new DHCP programs

Add the dhcpclient and dhcpserver binary files to the makefile and
file_contexts and give them the appropriate SELinux permissions to run.

BUG: 74514143
Test: Build emulator image and manually verify WiFi functionality
Change-Id: Ia472ef4c86c9b6ba967c0fc7443db607aed1e485
(cherry picked from commit 917bda2587d219e35404a298c05a7179519815c1)
(cherry picked from commit 87b9f937113801b50612863cb13e6391cc1f3105)
(cherry picked from commit 760a19890ac99144f6b143015c36e7aaa3797c73)