FIR: temporary implementation of kotlin.FunctionX resolve

compiler/testData/fir/resolve/stdlib/functionX.kt

@@ -0,0 +1,5 @@
+import kotlin.jvm.functions.Function0
+
+val x: Function0<Int> = { 42 }
+
+val y: Function1<String, String> = { it }

compiler/testData/fir/resolve/stdlib/functionX.txt

@@ -0,0 +1,5 @@
+FILE: functionX.kt
+    public? final? property x(val): R|kotlin/jvm/functions/Function0<kotlin/Int>| = STUB
+        public? get(): R|kotlin/jvm/functions/Function0<kotlin/Int>|
+    public? final? property y(val): R|kotlin/Function1<kotlin/String, kotlin/String>| = STUB
+        public? get(): R|kotlin/Function1<kotlin/String, kotlin/String>|