Introduce module 'reflection', move KFunctionN to it

Metadata for KFunction classes is now longer serialized along with built-in
classes. This effectively means that it's no longer possible to find KFunction
classes via dependency on built-ins. There should be a kotlin-runtime library
in the specified classpath for reflection types to be resolvable.

A lot of tests were moved and changed, because tests on callable references
require stdlib in classpath from now on

compiler/testData/diagnostics/testsWithStdLib/callableReference/function/topLevelFromExtension.kt

@@ -0,0 +1,15 @@
+class A
+
+fun foo() {}
+fun bar(<!UNUSED_PARAMETER!>x<!>: Int) {}
+fun baz() = "OK"
+
+fun A.main() {
+    val x = ::foo
+    val y = ::bar
+    val z = ::baz
+
+    x : KFunction0<Unit>
+    y : KFunction1<Int, Unit>
+    z : KFunction0<String>
+}