[JS IR] IC improvements

- Reuse a built fragment
  - Use cache for saving built JS code

js/js.translator/testData/incremental/invalidation/renameFile/main/m.kt

@@ -1,2 +1,5 @@
 
-fun box() = foo()
+fun box(): String {
+    if (foo() != 42) return "Fail"
+    return "OK"
+}

js/js.translator/testData/incremental/invalidation/renameFile/main/module.info

@@ -1,6 +1,5 @@
 STEP 0:
     dependencies: stdlib, lib1
     dirty: m.kt
-
 STEP 1:
-    dependencies: stdlib, lib1
+    dependencies: stdlib, lib1

js/js.translator/testData/incremental/invalidation/renameFile/project.info

@@ -2,6 +2,7 @@ MODULES: lib1, main
 
 STEP 0:
     libs: lib1, main
-
+    dirty js: stdlib, lib1, main
 STEP 1:
-    libs: lib1, main
+    libs: lib1, main
+    dirty js: lib1