Robust buffer access for vertex inputs/attributes
was not implemented. It's fixed in this cl by adding
robustBufferAccess to the Context structure, adding a
check in Renderer::advanceInstanceAttributes() to prevent
advancing a buffer past its end and adding out of bounds
checks in VertexRoutine::readStream()

This affects dEQP-VK.robustness.vertex_access.* tests,
which will be enabled when the vertexPipelineStoresAndAtomics
feature is turned on.

For now, this change should be noop in test results.

Bug b/140294254 b/131224163

Change-Id: Ib4d4cdb73f48495a556b6bd05b1d0e3ce800ad15
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/36268Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>