Basic implementation of descriptor update template.
Only supports VK_DESCRIPTOR_UPDATE_TEMPLATE_TYPE_DESCRIPTOR_SET template type.

Bug b/123244275

Change-Id: Iaf7c1e52bee6d2683a2f34bd2f780396aa953442
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/26568Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Chris Forbes <chrisforbes@google.com>