Revert "Update Readback VTS to align with RenderEngine interface..."

Revert "Update WaylandRenderSurface to accomodate interface change"

Revert "Add ExternalTexture class into RenderEngine interface"

Revert submission 14086921-renderengine-external-tex

Reason for revert: Potential culprit for b/185361988
Reverted Changes:
I7796764e2:Update WaylandRenderSurface to accomodate interfac...
I13904eec4:Update Readback VTS to align with RenderEngine int...
I222c71e6e:Add ExternalTexture class into RenderEngine interf...

Change-Id: I7d58118c1c2284a04eb52e992e901d82faaf5bb0
(cherry picked from commit 51daee61)