Convert FunctionBase to Kotlin, add type parameter to Lambda

This will make it possible to avoid raw types when inheriting from both
FunctionBase and Function<R>. This change adds a generic type parameter
to FunctionBase and Lambda which is not source-breaking under our policy
because both FunctionBase and Lambda are internal classes (located in
package kotlin.jvm.internal)

compiler/testData/codegen/box/callableReference/function/getArityViaFunctionImpl.kt

@@ -9,7 +9,7 @@ import kotlin.test.assertEquals
 import kotlin.jvm.internal.FunctionBase
 
 fun test(f: Function<*>, arity: Int) {
-    assertEquals(arity, (f as FunctionBase).getArity())
+    assertEquals(arity, (f as FunctionBase).arity)
 }
 
 fun foo(s: String, i: Int) {}