Report conflicting overloads for constructors

- It's worked almost fine but diagnostics were filtered out by
  positioning strategy.

- Also a couple of "put" calls to Multimap are replaced by "putValues"
  within OverloadResolver, that is more semantically correct.

- Note that constructors of top-level classes are handled when processing
  package, it helps to figure out if there are clashes with top-level
  functions that have the same name.

- But constructors of different classes are not reported as
  overloads because containing classes has the same name and will be
  reported as redeclaration.

compiler/testData/diagnostics/tests/secondaryConstructors/redeclarations.kt

@@ -0,0 +1,28 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+class <!CONFLICTING_OVERLOADS!>A(x: String = "", y: String = "")<!> {
+    <!CONFLICTING_OVERLOADS!>constructor(x: String, y: String)<!>: <!OVERLOAD_RESOLUTION_AMBIGUITY!>this<!>(x, y) {}
+    <!CONFLICTING_OVERLOADS!>constructor()<!>: <!OVERLOAD_RESOLUTION_AMBIGUITY!>this<!>("", "") {}
+    <!CONFLICTING_OVERLOADS!>constructor()<!>: <!OVERLOAD_RESOLUTION_AMBIGUITY!>this<!>("", "") {}
+}
+
+class B {
+    <!CONFLICTING_OVERLOADS!>constructor(x: Int)<!> {}
+}
+
+<!CONFLICTING_OVERLOADS!>fun B(x: Int)<!> {}
+
+class Outer {
+    class <!CONFLICTING_OVERLOADS!>A(x: String = "", y: String = "")<!> {
+        <!CONFLICTING_OVERLOADS!>constructor(x: String, y: String)<!>: <!OVERLOAD_RESOLUTION_AMBIGUITY!>this<!>(x, y) {}
+        <!CONFLICTING_OVERLOADS!>constructor()<!>: <!OVERLOAD_RESOLUTION_AMBIGUITY!>this<!>("", "") {}
+        <!CONFLICTING_OVERLOADS!>constructor()<!>: <!OVERLOAD_RESOLUTION_AMBIGUITY!>this<!>("", "") {}
+    }
+
+    class B {
+        <!CONFLICTING_OVERLOADS!>constructor(x: Int)<!> {
+        }
+    }
+
+    <!CONFLICTING_OVERLOADS!>fun B(x: Int)<!> {}
+}