The template-based descriptor write mechanism had got left behind as
more descriptor types were added. Reimplement the classic mechanism in
terms of a template entry, and implement all the current logic there.

Bug: b/123244275
Test: dEQP-VK.binding_model.*
Test: dEQP-VK.spirv_assembly.*
Test: dEQP-VK.glsl.*
Change-Id: Ide5a6bf70978774170f79d42652c746c2b5b8abd
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/29608Tested-by: Chris Forbes <chrisforbes@google.com>
Presubmit-Ready: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>