Generate bridges for property accessors

Use existing FunctionCodegen.generateBridgeIfNeeded() on property getters &
setters

 #KT-2920 Fixed

compiler/testData/codegen/bridges/propertyAccessorsWithoutBody.kt

@@ -0,0 +1,15 @@
+open class A<T> {
+    open var x: T = "Fail" as T
+    get
+}
+
+class B : A<String>() {
+    override var x: String = "Fail"
+    set
+}
+
+fun box(): String {
+    val a: A<String> = B()
+    a.x = "OK"
+    return a.x
+}

compiler/testData/codegen/bridges/propertyDiamond.kt

@@ -0,0 +1,18 @@
+trait A<O, K> {
+    val o: O
+    val k: K
+}
+
+trait B<K> : A<String, K>
+
+trait C<O> : A<O, String>
+
+class D : B<String>, C<String> {
+    override val o = "O"
+    override val k = "K"
+}
+
+fun box(): String {
+    val a: A<String, String> = D()
+    return a.o + a.k
+}

compiler/testData/codegen/bridges/propertySetter.kt

@@ -0,0 +1,13 @@
+trait A<T> {
+    var v: T
+}
+
+class B : A<String> {
+    override var v: String = "Fail"
+}
+
+fun box(): String {
+    val a: A<String> = B()
+    a.v = "OK"
+    return a.v
+}

compiler/testData/codegen/bridges/substitutionInSuperClassProperty.kt

@@ -0,0 +1,12 @@
+open class A<T>(val t: T) {
+    open val foo: T = t
+}
+
+open class B : A<String>("Fail")
+
+class Z : B() {
+    override val foo = "OK"
+}
+
+
+fun box() = (Z() : A<String>).foo

compiler/testData/codegen/regressions/kt2920.kt

@@ -0,0 +1,9 @@
+trait Tr<T> {
+    val v: T
+}
+
+class C : Tr<String> {
+    override val v = "OK"
+}
+
+fun box() = C().v