[JS IR] IC improvements

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

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

@@ -0,0 +1,12 @@
+
+fun box(stepId: Int): String {
+    when (stepId) {
+        0 -> if (qux() != 44) return "Fail"
+        1 -> if (qux() != 66) return "Fail"
+        2 -> if (qux() != 40) return "Fail"
+        3 -> if (qux() != 18) return "Fail"
+        4 -> if (qux() != 14) return "Fail"
+        else -> return "Unknown"
+    }
+    return "OK"
+}

js/js.translator/testData/incremental/invalidation/crossModuleReferences/main/m.kt.5.txt

@@ -0,0 +1,11 @@
+
+fun box(stepId: Int): String {
+    when (stepId) {
+        5 -> if (qux() != 14) return "Fail"
+        6 -> if (qux() != 104) return "Fail"
+        else -> return "Unknown"
+    }
+    if (baz(77) != 79) return "Fail"
+    if (baz("test") != 4) return "Fail"
+    return "OK"
+}

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

@@ -0,0 +1,12 @@
+STEP 0:
+    dependencies: stdlib, lib1, lib2
+    dirty: m.kt
+STEP 1..4:
+    dependencies: stdlib, lib1, lib2
+STEP 5:
+    dependencies: stdlib, lib1, lib2
+    modifications:
+        U : m.kt.5.txt -> m.kt
+    dirty: m.kt
+STEP 6:
+    dependencies: stdlib, lib1, lib2