[JS IR] Lift lambdas that capture no context

If a lambda expression does not capture any local variables, convert
it to a global free function and replace the lambda creation with
a reference to that function.

Example: for the following Kotlin code

```kotlin
fun foo(f: () -> Unit) = f()

fun bar() = foo { console.log("hello") }
```

before this patch, we generated:

```js
function foo(f) {
  return f();
}
function bar() {
  return foo(bar$lambda());
}
function bar$lambda() {
  return function () {
    console.log('hello');
  };
}
```

after this patch, we generate:

```js
function foo(f) {
  return f();
}
function bar() {
  return foo(bar$lambda);
}
function bar$lambda() {
  console.log('hello');
}
```

compiler/testData/codegen/box/when/enumOptimization/manyWhensWithinClass.kt

@@ -2,7 +2,7 @@
 // CHECK_CASES_COUNT: function=bar1_u51tkt$ count=3 TARGET_BACKENDS=JS
 // CHECK_IF_COUNT: function=bar1_u51tkt$ count=0 TARGET_BACKENDS=JS
 // CHECK_CASES_COUNT: function=A$bar2$lambda count=3 TARGET_BACKENDS=JS
-// CHECK_CASES_COUNT: function=A$bar2$lambda count=0 IGNORED_BACKENDS=JS
+// CHECK_CASES_COUNT: function=A$bar2$lambda count=4 IGNORED_BACKENDS=JS
 // CHECK_IF_COUNT: function=A$bar2$lambda count=0
 
 import kotlin.test.assertEquals