[JS IR] Lower lambdas into in-line anonymous functions when possible

Previously we always generated factories for contextful lambdas:

```kt
fun foo(a: Int) = { a }
```

```js
function foo(a_38) {
  return foo$lambda(a_38);
}

// factory!
function foo$lambda($a) {
  return function () {
    return $a;
  };
}
```

After this patch, the generated code for `foo` is more concise:

```js
function foo(a) {
  return function() { return a; };
}
```

js/js.translator/testData/box/closure/closureCodeSize.kt

@@ -0,0 +1,60 @@
+// KT-51133
+
+package foo
+
+fun <T, R> myWith(t: T, f: (T) -> R) = f(t)
+
+// CHECK_CONTAINS_NO_CALLS: noCapture except=myWith
+// HAS_NO_CAPTURED_VARS: function=noCapture except=myWith;noCapture$lambda
+fun noCapture() = myWith(42) { it }
+
+// CHECK_CONTAINS_NO_CALLS: captureLocalVariableReadOnly except=myWith IGNORED_BACKENDS=JS
+// HAS_NO_CAPTURED_VARS: function=captureLocalVariableReadOnly except=myWith IGNORED_BACKENDS=JS
+fun captureLocalVariableReadOnly(a: Int) = myWith(1) { a + it }
+
+// CHECK_CONTAINS_NO_CALLS: captureLocalVariableReadWrite except=myWith IGNORED_BACKENDS=JS
+// HAS_NO_CAPTURED_VARS: function=captureLocalVariableReadWrite except=myWith IGNORED_BACKENDS=JS
+fun captureLocalVariableReadWrite(): Int {
+    var a = 41
+    return myWith(1) {
+        a += it
+        a
+    }
+}
+
+val thirteen = 13
+
+// CHECK_CONTAINS_NO_CALLS: captureGlobalVariable except=myWith
+// HAS_NO_CAPTURED_VARS: function=captureGlobalVariable except=myWith;captureGlobalVariable$lambda
+fun captureGlobalVariable() = myWith(2) { thirteen * it }
+
+class A(val i: Int) {
+
+    fun captureClassField() = myWith(100) { it + i }
+
+    inner class B(val j: Int) {
+
+        inner class C(val k: Int) {
+            fun captureInnerClassField() = myWith(200) { it + i + j + k }
+
+            fun unusedLambda() {
+                { i + j + k }
+            }
+        }
+    }
+}
+
+fun unusedLambda(f: () -> Unit) {
+    { f() }
+}
+
+fun box(): String {
+    if (noCapture() != 42) return "fail noCapture()"
+    if (captureLocalVariableReadOnly(41) != 42) return "fail captureLocalVariableReadOnly(41)"
+    if (captureLocalVariableReadWrite() != 42) return "fail captureLocalVariableReadWrite()"
+    if (captureGlobalVariable() != 26) return "fail captureGlobalVariable()"
+    if (A(23).captureClassField() != 123) return "fail A(23).captureClassField()"
+    if (A(300).B(400).C(500).captureInnerClassField() != 1400) return "A(300).B(400).C(500).captureInnerClassField()"
+
+    return "OK"
+}