[FIR] Add diagnostic CONFLICTING_OVERLOADS & REDECLARATION

compiler/testData/diagnostics/tests/dataClasses/conflictingCopyOverloads.fir.kt

@@ -1,6 +1,6 @@
 // !DIAGNOSTICS: -UNUSED_PARAMETER
 
 data class A(val x: Int, val y: String) {
-    fun copy(x: Int, y: String) = x
-    fun copy(x: Int, y: String) = A(x, y)
+    <!CONFLICTING_OVERLOADS!>fun copy(x: Int, y: String) = x<!>
+    <!CONFLICTING_OVERLOADS!>fun copy(x: Int, y: String) = A(x, y)<!>
 }

compiler/testData/diagnostics/tests/dataClasses/repeatedProperties.fir.kt

@@ -1,9 +1,9 @@
-data class A1(val x: Int, val y: String, val x: Int) {
+data class A1(<!REDECLARATION!>val x: Int<!>, val y: String, <!REDECLARATION!>val x: Int<!>) {
     val z = ""
 }
 
-data class A2(val x: Int, val y: String) {
-    val x = ""
+data class A2(<!REDECLARATION!>val x: Int<!>, val y: String) {
+    <!REDECLARATION!>val x = ""<!>
 }
 
-data class A3(val<!SYNTAX!><!> :Int, val<!SYNTAX!><!> : Int)
+data class A3(<!REDECLARATION!>val<!SYNTAX!><!> :Int<!>, <!REDECLARATION!>val<!SYNTAX!><!> : Int<!>)