FIR checker: introduce DECLARATION_SIGNATURE_OR_DEFAULT positioning strategy

and fix CONFLICTING_OVERLOADS to use it

compiler/testData/diagnostics/tests/overload/ConflictingOverloadsFunsDifferentReturnInClass.fir.kt

@@ -1,6 +1,6 @@
 class A {
-    <!CONFLICTING_OVERLOADS!>fun a(a: Int): Int = 0<!>
+    <!CONFLICTING_OVERLOADS!>fun a(a: Int): Int<!> = 0
 
-    <!CONFLICTING_OVERLOADS!>fun a(a: Int) {
-    }<!>
+    <!CONFLICTING_OVERLOADS!>fun a(a: Int)<!> {
+    }
 }

compiler/testData/diagnostics/tests/overload/ConflictingOverloadsFunsDifferentReturnInPackage.fir.kt

@@ -1,7 +1,7 @@
 package qwertyuiop
 
-<!CONFLICTING_OVERLOADS!>fun c(s: String) {
-}<!>
+<!CONFLICTING_OVERLOADS!>fun c(s: String)<!> {
+}
 
-<!CONFLICTING_OVERLOADS!>fun c(s: String) {
-}<!>
+<!CONFLICTING_OVERLOADS!>fun c(s: String)<!> {
+}

compiler/testData/diagnostics/tests/overload/ConflictingOverloadsIdenticalExtFunsInPackage.fir.kt

@@ -1,5 +1,5 @@
 package extensionFunctions
 
-<!CONFLICTING_OVERLOADS!>fun Int.qwe(a: Float) = 1<!>
+<!CONFLICTING_OVERLOADS!>fun Int.qwe(a: Float)<!> = 1
 
-<!CONFLICTING_OVERLOADS!>fun Int.qwe(a: Float) = 2<!>
+<!CONFLICTING_OVERLOADS!>fun Int.qwe(a: Float)<!> = 2

compiler/testData/diagnostics/tests/overload/ConflictingOverloadsIdenticalFunsInClass.fir.kt

@@ -1,7 +0,0 @@
-class A() {
-    <!CONFLICTING_OVERLOADS!>fun b() {
-    }<!>
-
-    <!CONFLICTING_OVERLOADS!>fun b() {
-    }<!>
-}

compiler/testData/diagnostics/tests/overload/ConflictingOverloadsIdenticalFunsInClass.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 class A() {
     <!CONFLICTING_OVERLOADS!>fun b()<!> {
     }

compiler/testData/diagnostics/tests/overload/TypeParameterMultipleBounds.fir.kt

@@ -1,15 +0,0 @@
-import java.io.Serializable
-
-interface Test1 {
-    <!CONFLICTING_OVERLOADS!>fun <T> foo(t: T) where T : Cloneable, T : Serializable<!>
-    <!CONFLICTING_OVERLOADS!>fun <T> foo(t: T) where T : Serializable, T : Cloneable<!>
-}
-
-
-interface I1
-interface I2 : I1
-
-interface Test2 {
-    <!CONFLICTING_OVERLOADS!>fun <T> foo(t: T) where T : I1, T : I2<!>
-    <!CONFLICTING_OVERLOADS!>fun <T> foo(t: T) where T : I2, T : I1<!>
-}

compiler/testData/diagnostics/tests/overload/TypeParameterMultipleBounds.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 import java.io.Serializable
 
 interface Test1 {