Client can specify array slice for creating the SRV/RTV with
EGL_D3D11_TEXTURE_ARRAY_SLICE_ANGLE.

Test: D3DTextureTest.TextureArrayImage*
Bug: angleproject:5538, chromium:1116101
Change-Id: I81cb2823df2145f1d05ad1526b0e36d6a0724d5e
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2628609Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Sunny Sachanandani <sunnyps@chromium.org>