[JS IR] IC improvements

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

js/js.translator/testData/incremental/invalidation/crossModuleReferences/lib2/l2.kt

@@ -0,0 +1,2 @@
+
+fun qux() = foo() + 2

js/js.translator/testData/incremental/invalidation/crossModuleReferences/lib2/l2.kt.1.txt

@@ -0,0 +1,2 @@
+
+fun qux() = foo() + bar()

js/js.translator/testData/incremental/invalidation/crossModuleReferences/lib2/l2.kt.2.txt

@@ -0,0 +1,2 @@
+
+fun qux() = foo() - 2

js/js.translator/testData/incremental/invalidation/crossModuleReferences/lib2/l2.kt.3.txt

@@ -0,0 +1,2 @@
+
+fun qux() = baz(2) + baz("test") + baz(true)

js/js.translator/testData/incremental/invalidation/crossModuleReferences/lib2/l2.kt.4.txt

@@ -0,0 +1,2 @@
+
+fun qux() = baz("test") + baz(true)

js/js.translator/testData/incremental/invalidation/crossModuleReferences/lib2/l2.kt.6.txt

@@ -0,0 +1,2 @@
+
+fun qux() = baz("test") + 100

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

@@ -0,0 +1,31 @@
+STEP 0:
+    dependencies: stdlib, lib1
+    dirty: l2.kt
+STEP 1:
+    dependencies: stdlib, lib1
+    modifications:
+        U : l2.kt.1.txt -> l2.kt
+    dirty: l2.kt
+STEP 2:
+    dependencies: stdlib, lib1
+    modifications:
+        U : l2.kt.2.txt -> l2.kt
+    dirty: l2.kt
+STEP 3:
+    dependencies: stdlib, lib1
+    modifications:
+        U : l2.kt.3.txt -> l2.kt
+    dirty: l2.kt
+STEP 4:
+    dependencies: stdlib, lib1
+    modifications:
+        U : l2.kt.4.txt -> l2.kt
+    dirty: l2.kt
+STEP 5:
+    dependencies: stdlib, lib1
+    flags: FP
+STEP 6:
+    dependencies: stdlib, lib1
+    modifications:
+        U : l2.kt.6.txt -> l2.kt
+    dirty: l2.kt