Migrate apex/sdkextensions to packages/modules/SdkExtensions

BUG: 156286599
Test: TH and Forrest (mainline_modules)
Merged-In: I0009d286205d7942c2d681936bfba38e074700d2
Change-Id: I8a3d00da1528dee22839ac0997505d20c8bfe10e
25 files changed