Add NUM_VALUES for enums and size for structs (see #3836)

API versioning requires that enumerations end with a count value
(`*_NUM_VALUES`) and structs begin with a size value (`size_t size`).
Wrapper templates are updated to support structs with different size
values indicating different versions.

To test:
Run `ceftests --gtest_filter=ApiVersionTest.StructVersion*`

tests/cefclient/browser/test_runner.cc

@@ -775,6 +775,8 @@ std::string GetErrorString(cef_termination_status_t status) {
       return "LAUNCH_FAILED";
     case TS_INTEGRITY_FAILURE:
       return "INTEGRITY_FAILURE";
+    case TS_NUM_VALUES:
+      break;
   }
   NOTREACHED();
   return std::string();