fix incorrect overload error on regular function and extension function with same name

===
fun ff() = 1

fun Int.ff() = 1
===

compiler/testData/checkerWithErrorTypes/quick/ConflictingOverloads.jet

@@ -46,3 +46,22 @@ namespace ns3 {
     }
 }
 
+// check same rules apply for ext functions
+
+namespace extensionFunctions {
+    <!CONFLICTING_OVERLOADS!>fun Int.qwe(a: Float)<!> = 1
+    
+    <!CONFLICTING_OVERLOADS!>fun Int.qwe(a: Float)<!> = 2
+    
+    fun Int.rty() = 3
+    
+    fun String.rty() = 4
+}
+
+// check no error when regular function and extension function have same name
+
+namespace extensionAndRegular {
+    fun who() = 1
+    
+    fun Int.who() = 1
+}