Fix VerifyError on primitive override properties

Don't just blindly map property type in PropertyCodegen when generating getter:
we already have its full signature, so we can just as well take the type from
it. The former also isn't correct for properties which are overrides with a
primitive type. Simple mapType is safe for setter though, because the type of a
method parameter cannot change with override on JVM

The change in StackValue relates to call sites of properties which return Unit:
in that case StackValue's this.type is V, whereas the return type of its getter
is Ljet/Unit; -- so coerceTo was coercing from the wrong type in case of getter
calls

 #KT-4373 Fixed
 #KT-4383 Fixed

compiler/testData/codegen/box/properties/kt4373.kt

@@ -0,0 +1,14 @@
+trait Tr<T> {
+    val prop: T
+}
+
+class A(a: Tr<Int>) : Tr<Int> by a
+
+fun eat(x: Int) {}
+
+fun box(): String {
+    eat(A(object : Tr<Int> {
+        override val prop = 42
+    }).prop)
+    return "OK"
+}