Fix nonsemantic debuginfo line attribution for cooperative matrix

* Generate debuginfo for coopmat types, treating them as an opaque composite. Restore the debug source location after calling convertGlslangToSpvType, fixes the line info in this unit test

* Add a cooperative matrix test case, based on the shader from https://github.com/jeffbolznv/vk_cooperative_matrix_perf/blob/master/shaders/shmem.comp

gtests/Spv.FromFile.cpp

@@ -959,6 +959,7 @@ INSTANTIATE_TEST_SUITE_P(
         "spv.debuginfo.include.glsl.frag",
         "spv.debuginfo.multiline.glsl.frag",
         "spv.debuginfo.implicit_br.glsl.frag",
+        "spv.debuginfo.coopmatKHR.comp",
     })),
     FileNameAsCustomTestSuffix
 );