KT-14400: Properly handle TypeAliasConstructorDescriptor in KotlinTypeMapper.mapToCallableMethod(...)

Implement getDefaultType() in TypeAliasDescriptor subclasses.

compiler/testData/diagnostics/tests/typealias/typeAliasInAnonymousObjectType.kt

@@ -0,0 +1,5 @@
+open class Foo<T>
+
+typealias FooStr = Foo<String>
+
+val test = object : FooStr() {}

compiler/testData/diagnostics/tests/typealias/typeAliasInAnonymousObjectType.txt

@@ -0,0 +1,11 @@
+package
+
+public val test: FooStr /* = Foo<kotlin.String> */
+
+public open class Foo</*0*/ T> {
+    public constructor Foo</*0*/ T>()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+public typealias FooStr = Foo<kotlin.String>