Autodetect if modules hook is needed

nodejs/packages/layer/scripts/otel-handler

@@ -3,8 +3,11 @@
 echo "LAMBDA_TASK_ROOT=${LAMBDA_TASK_ROOT}"
 echo "_HANDLER=${_HANDLER}"
 
+possible_mjs_handler_file="${LAMBDA_TASK_ROOT}/${_HANDLER%.*}.mjs"
+echo "possible_mjs_handler_file=${possible_mjs_handler_file}"
+
 # If the handler is in an .mjs file we need to use a loader hook. We can't detect it here because the corresponding env vars are not available at this point
-if [ "$OTEL_NODEJS_HOOK" == "modules" ]; then
+if [ "$OTEL_NODEJS_HOOK" == "modules" ] || [ -f "$possible_mjs_handler_file" ]; then
     export NODE_OPTIONS="${NODE_OPTIONS} --experimental-loader=@opentelemetry/instrumentation/hook.mjs"
     # Disable node warnings caused by --experimental-loader
     export NODE_NO_WARNINGS=1