fix(pack): simplify async externals script chunk filename

crates/pack-tests/tests/snapshot/externals/basic/output/main.js

@@ -1,5 +1,5 @@
 (globalThis["TURBOPACK"] || (globalThis["TURBOPACK"] = [])).push([
     typeof document === "object" ? document.currentScript : undefined,
-    {"otherChunks":["_root-of-the-server___a4c79e8f.js"],"runtimeModuleIds":[212]}
+    {"otherChunks":["_root-of-the-server___3b647096.js"],"runtimeModuleIds":[212]}
 ]);
 // Dummy runtime

crates/pack-tests/tests/snapshot/externals/script/config.json

@@ -0,0 +1,17 @@
+{
+    "config": {
+        "entry": [
+            {
+                "import": "input/index.ts",
+                "name": "main"
+            }
+        ],
+        "externals": {
+            "lodash": {
+                "root": "_",
+                "type": "script",
+                "script": "https://gw.alipayobjects.com/os/lib/lodash/4.17.21/lodash.min.js"
+            }
+        }
+    }
+}

crates/pack-tests/tests/snapshot/externals/script/input/index.ts

@@ -0,0 +1,6 @@
+const func = async () => {
+    // @ts-ignore
+    const _ = await import('lodash');
+    console.log(Object.keys(_.default.omit({ a: 1 }, 'a')).length === 0);
+};
+func();

crates/pack-tests/tests/snapshot/externals/script/output/_externals____2fc6bb03.js

@@ -0,0 +1,21 @@
+(globalThis["TURBOPACK"] || (globalThis["TURBOPACK"] = [])).push([typeof document === "object" ? document.currentScript : undefined,
+20, ((__turbopack_context__) => {
+"use strict";
+
+return __turbopack_context__.a(async (__turbopack_handle_async_dependencies__, __turbopack_async_result__) => { try {
+
+let mod;
+try {
+  await __turbopack_context__.L("https://gw.alipayobjects.com/os/lib/lodash/4.17.21/lodash.min.js");
+  if (typeof global["_"] === 'undefined') {
+    throw new Error('Variable "_" is not available on global object after loading "https://gw.alipayobjects.com/os/lib/lodash/4.17.21/lodash.min.js"');
+  }
+  mod = global["_"];
+} catch (error) {
+  throw new Error('Failed to load external URL module "_@https://gw.alipayobjects.com/os/lib/lodash/4.17.21/lodash.min.js": ' + (error.message || error));
+}
+
+__turbopack_context__.v(mod);
+__turbopack_async_result__();
+} catch(e) { __turbopack_async_result__(e); } }, true);}),
+]);

crates/pack-tests/tests/snapshot/externals/script/output/main.js

@@ -0,0 +1,5 @@
+(globalThis["TURBOPACK"] || (globalThis["TURBOPACK"] = [])).push([
+    typeof document === "object" ? document.currentScript : undefined,
+    {"otherChunks":["_root-of-the-server___7ced73a1.js"],"runtimeModuleIds":[19]}
+]);
+// Dummy runtime