D3D11: Translate uniform blocks to StructuredBuffer when necessary fxc exhibits slow compile performance with dynamic cbuffer indexing. So when a uniform block contains only one large array member, which is an array of structures, translate this uniform block to a StructuredBuffer instead. Bug: angleproject:3682 TEST=angle_end2end_tests.UniformBufferTest.* Change-Id: Ife80dba8aae65b761737e095895e00a570230f88 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1782046 Commit-Queue: Xinghua Cao <xinghua.cao@intel.com> Reviewed-by: Kenneth Russell <kbr@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>