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/Compiler.cpp b/lib/Compiler.cpp
index 0b1a6ce..1971b26 100644
--- a/lib/Compiler.cpp
+++ b/lib/Compiler.cpp
@@ -603,6 +603,7 @@
 
   pm->add(clspv::createZeroInitializeAllocasPass());
   pm->add(clspv::createAddFunctionAttributesPass());
+  pm->add(clspv::createAutoPodArgsPass());
   pm->add(clspv::createDeclarePushConstantsPass());
   pm->add(clspv::createDefineOpenCLWorkItemBuiltinsPass());