Rev up vr_hwc to composer@2.3

Fix for issue: "[GSI XR] VrFlinger doesn't work on GSI/MTP845.

Making member variables protected instead of private for the 2.3
interface, which is the behavior in the 2.1 interface.
"vr_composer_client" needs to access the "mResources" and "mHal" class
member to be able to create the ComposerCommandEngine.

Bug: 137325030
Bug: 138938154
Bug: 137448042

Test: Built the firmware and ran the dvr_display-test, which passes
now.

Change-Id: I0f531d4dd6d60a3f2da793f19b4d3ea1eb53930e