[JS IR] IC improvements

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

js/js.translator/testData/incremental/invalidation/removeFile/lib2/module.info

@@ -1,8 +1,7 @@
 STEP 0:
     dependencies: stdlib, lib1
     dirty: l2_0.kt, l2_1.kt
-
 STEP 1:
     dependencies: stdlib, lib1
     modifications:
-        D : l2_1.kt
+        D : l2_1.kt

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

@@ -1,2 +1,6 @@
 
-fun box() = qux0() + qux1()
+fun box(): String {
+    if (qux0() != 42) return "Fail"
+    if (qux1() != 24) return "Fail"
+    return "OK"
+}

js/js.translator/testData/incremental/invalidation/removeFile/main/m.kt.new

@@ -1,2 +1,5 @@
 
-fun box() = qux0()
+fun box(): String {
+    if (qux0() != 42) return "Fail"
+    return "OK"
+}

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

@@ -1,9 +1,8 @@
 STEP 0:
     dependencies: stdlib, lib1, lib2
     dirty: m.kt
-
 STEP 1:
     dependencies: stdlib, lib1, lib2
     modifications:
         U : m.kt.new -> m.kt
-    dirty: m.kt
+    dirty: m.kt

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

@@ -2,6 +2,7 @@ MODULES: lib1, lib2, main
 
 STEP 0:
     libs: lib1, lib2, main
-
+    dirty js: stdlib, lib1, lib2, main
 STEP 1:
-    libs: lib1, lib2, main
+    libs: lib1, lib2, main
+    dirty js: lib1, lib2, main