Refactor external overidability conditions

Before this change they could only negatively affect on result
Now they may force success result

Also refine overridavility condition for java fields:
two java fields having the same name are seen as overrides even
if they have different type

compiler/testData/diagnostics/tests/j+k/fieldOverridesFieldOfDifferentType.kt

@@ -0,0 +1,19 @@
+// !CHECK_TYPE
+
+// FILE: A.java
+
+public class A {
+    public int size = 1;
+}
+
+// FILE: B.java
+
+public class B extends A {
+    public String size = 1;
+}
+
+// FILE: main.kt
+
+fun foo() {
+    B().size.checkType { _<String>() }
+}

compiler/testData/diagnostics/tests/j+k/fieldOverridesFieldOfDifferentType.txt

@@ -0,0 +1,19 @@
+package
+
+public fun foo(): kotlin.Unit
+
+public open class A {
+    public constructor A()
+    public final var size: kotlin.Int
+    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 open class B : A {
+    public constructor B()
+    public final override /*1*/ var size: kotlin.String
+    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
+}