VK_EXT_image_robustness requires loads and stores using a pointer
produced by OpImageTexelPointer to be bounds checked. Out-of-bounds
reads must result in [0,0,0,0] or [0,0,0,1] values. We always return
all-zero. Out-of-bounds writes must be ignored.

This also includes the read-modify-write operations performed by atomic
instructions.

Bug: b/159329067
Tests: dEQP-VK.robustness.image_robustness.*
Change-Id: I4f5c2e8ae0bc89e61207fd1f7f1c449a35ca621e
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/47069
Presubmit-Ready: Nicolas Capens <nicolascapens@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>