Automate pod arg implementation decision (#575)

Contributes to #529

* Decision made on a per-kernel basis
* New pass assigns metadata to kernels
  * passes use that metadata through new utliities to get the right
  ArgKinds
  * currently only decides based on command line options (so NFC)
* Refactored layout validation into new files
* Refactored some global push constant methods
* new enum for how pod args are implemented
  * kGlobalPushConstant will be implemented in the future
* added new metadata to test that required it
* changed arg kind utility to take the arg instead of just the type
* Priorities per-kernel push constants then ubo then ssbo
  * checks for compatibility
* Added new variant of isValidExplicitLayout that checks the whole
struct
diff --git a/lib/DirectResourceAccessPass.cpp b/lib/DirectResourceAccessPass.cpp
index b6d1032..4f36567 100644
--- a/lib/DirectResourceAccessPass.cpp
+++ b/lib/DirectResourceAccessPass.cpp
@@ -105,7 +105,7 @@
   bool Changed = false;
   int arg_index = 0;
   for (Argument &arg : fn->args()) {
-    switch (clspv::GetArgKindForType(arg.getType())) {
+    switch (clspv::GetArgKind(arg)) {
     case clspv::ArgKind::Buffer:
     case clspv::ArgKind::BufferUBO:
     case clspv::ArgKind::ReadOnlyImage: