This patch adds the link validation on the maximum combined shader
output resources required in OpenGL ES 3.1 SPEC.

OpenGL ES 3.1 SPEC has restrictions on the sum of the number of all
active images, shader storage blocks and fragment shader outputs. A
link error will be generated if this sum exceeds the implementation-
dependent value of MAX_COMBINED_SHADER_OUTPUT_RESOURCES.

In order not to affect the existing image tests, this patch also
sets a temporary value for maxCombinedShaderOutputResources on D3D11
back-ends. We will set more accurate values for all the UAV related
resource limits in the next patch.

BUG=angleproject:2345
TEST=dEQP-GLES31.functional.state_query.integer.max_combined_shader_output_resources_*

Change-Id: Ib83a19ef0ae0b9af3422b5c970c7c07d96b2359d
Reviewed-on: https://chromium-review.googlesource.com/1039155
Commit-Queue: Jiawei Shao <jiawei.shao@intel.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>