Generate bridges for trait implementations properly

The intent was to keep the bridge codegen model as simple as possible: we
should be able to figure out all necessary bridges only by a minimal interface
that FunctionHandle provides (isAbstract, isDeclaration, getOverridden)

Add different tests for bridges

 #KT-318 Obsolete

compiler/testData/codegen/box/bridges/kt318.kt

@@ -0,0 +1,23 @@
+var result = ""
+
+trait Base
+open class Child : Base
+
+trait A<T : Base> {
+    fun <E : T> foo(a : E) {
+        result += "A"
+    }
+}
+
+class B : A<Child> {
+    override fun <E : Child> foo(a : E) {
+        result += "B"
+    }
+}
+
+fun box(): String {
+    val b = B()
+    b.foo(Child())
+    (b : A<Child>).foo(Child())
+    return if (result == "BB") "OK" else "Fail: $result"
+}