add testing for SPIR-V 1.5 (#2208)

fixes #2140 

Adds testing for SPIR-V 1.5 features:

* Adds a test for bitcasts between pointers and vectors of integers.
Note, SPIR-V 1.5 only supports bitcasts to vectors of two 32-bit
integers. Therefore, the SPIR-V 1.5 behavior will only be exercised on
devices with 64-bit pointers. The test will run on devices with 32-bit
pointers, but will instead bitcast to scalars.
* Adds a test for OpGroupNonUniformBroadcast with a dynamic index. Note,
this is not an exhaustive test, and only unsigned integer types are
tested, to avoid duplicating testing for cl_khr_subgroup_ballot.

test_conformance/spirv_new/CMakeLists.txt

@@ -28,6 +28,7 @@ set(${MODULE_NAME}_SOURCES
   test_op_vector_insert.cpp
   test_op_vector_times_scalar.cpp
   test_spirv_14.cpp
+  test_spirv_15.cpp
 )
 
 set(TEST_HARNESS_SOURCES