Skip network validation if validated recently upon switching

Have a fixed sized cache of validated networks in ValidatedNetworkCache.

Bug: 140070796
Test: unittest
Change-Id: I5f7f3880d02afcb70f9b591bdc02e818488989a1
Merged-In: I5f7f3880d02afcb70f9b591bdc02e818488989a1
2 files changed