This uses the new classes introduced in ResourceManager11. Smart
pointers mean we can use ANGLE_TRY in more places, and don't need
to manually release these views. There is now a single point in the
D3D11 back-end where depth stencil views are allocated.

BUG=angleproject:2034

Change-Id: If0de2529ece1298e8babf24c07cc4be9849cc4de
Reviewed-on: https://chromium-review.googlesource.com/503249Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>