Split client and server impl

Some of the code in VHAL client implementation contains Android-specific
code, and some of the server operations only works in the native case.
So we split them up so that the AGL VHAL server can selectivly pick the
parts it needs.

It won't change the logic of native VHAL.

Bug: 148877226
Bug: 150791171

Test: Build

Change-Id: Ie142b19a5c435a0b4252ffd297504bde69eb44b0
(cherry picked from commit 7e9e37fa)
Merged-In: Ie142b19a5c435a0b4252ffd297504bde69eb44b0