KT-5963 Call to super shouldn't require type specification if there is no conflict

Implemented unqualified 'super' type resolution (in BasicExpressionTypingVisitor).

No overload resolution of any kind is involved.
Corresponding supertype is determined by the expected member name only:
- 'super.foo(...)' - function or property (of possibly callable type) 'foo'
- 'super.x' - property 'x'
Supertype should provide a non-abstract implementation of such member.
As a fall-back solution for diagnostics purposes, consider supertypes with abstract implementation of such member.

Diagnostics:
- AMBIGUOUS_SUPER on 'super', if multiple possible supertypes are available;
- ABSTRACT_SUPER_CALL on selector expression, if the only available implementation is abstract.

#KT-5963 Fixed

compiler/testData/codegen/box/super/unqualifiedSuper.kt

@@ -0,0 +1,66 @@
+open class Base() {
+    open fun baseFun(): String = "Base.baseFun()"
+
+    open fun unambiguous(): String = "Base.unambiguous()"
+
+    open val baseProp: String
+        get() = "Base.baseProp"
+}
+
+interface Interface {
+    fun interfaceFun(): String = "Interface.interfaceFun()"
+
+    fun unambiguous(): String // NB abstract
+}
+
+interface AnotherInterface
+
+interface DerivedInterface: Interface, AnotherInterface {
+    override fun interfaceFun(): String = "DerivedInterface.interfaceFun()"
+
+    override fun unambiguous(): String = "DerivedInterface.unambiguous()"
+
+    fun callsFunFromSuperInterface(): String = super.interfaceFun()
+}
+
+class Derived : Base(), Interface {
+    override fun baseFun(): String = "Derived.baseFun()"
+
+    override fun unambiguous(): String = "Derived.unambiguous()"
+
+    override fun interfaceFun(): String = "Derived.interfaceFun()"
+
+    override val baseProp: String
+        get() = "Derived.baseProp"
+
+    fun callsBaseFun(): String = super.baseFun()
+
+    fun callsUnambiguousFun(): String = super.unambiguous()
+
+    fun getsBaseProp(): String = super.baseProp
+
+    fun callsInterfaceFun(): String = super.interfaceFun()
+}
+
+fun box(): String {
+    val d = Derived()
+
+    val test1 = d.callsBaseFun()
+    if (test1 != "Base.baseFun()") return "Failed: d.callsBaseFun()==$test1"
+
+    val test2 = d.callsUnambiguousFun()
+    if (test2 != "Base.unambiguous()") return "Failed: d.callsUnambiguousFun()==$test2"
+
+    val test3 = d.getsBaseProp()
+    if (test3 != "Base.baseProp") return "Failed: d.getsBaseProp()==$test3"
+
+    val test4 = d.callsInterfaceFun()
+    if (test4 != "Interface.interfaceFun()") return "Failed: d.callsInterfaceFun()==$test4"
+
+    val di = object : DerivedInterface {}
+
+    val test5 = di.callsFunFromSuperInterface()
+    if (test5 != "Interface.interfaceFun()") return "Failed: di.callsFunFromSuperInterface()==$test5"
+
+    return "OK"
+}