Emit correct nonsemantic debug info for explicitly sized types

Previously, the type names in the nonsemantic shader debug info would be
"int", "uint", or "float" for all numeric types. This change makes the
correct names such as "int8_t" or "float16_t" get emitted.

gtests/Spv.FromFile.cpp

@@ -902,7 +902,8 @@ INSTANTIATE_TEST_SUITE_P(
         "spv.debuginfo.glsl.geom",
         "spv.debuginfo.glsl.tesc",
         "spv.debuginfo.glsl.tese",
-        "spv.debuginfo.const_params.glsl.comp"
+        "spv.debuginfo.const_params.glsl.comp",
+        "spv.debuginfo.scalar_types.glsl.frag",
     })),
     FileNameAsCustomTestSuffix
 );