Report resolution ambiguity on '+=' by taking into account full resolution result including post type checking for '+'

^KT-45503 Fixed

compiler/testData/diagnostics/tests/operatorsOverloading/plusAssignOnVarAndCollections.fir.kt

@@ -0,0 +1,31 @@
+// WITH_RUNTIME
+
+fun test1() {
+    var list = ArrayList<Int>()
+    <!ASSIGN_OPERATOR_AMBIGUITY!>list -= 2<!>
+}
+
+fun test2() {
+    var set = HashMap<Int, Int>()
+    <!ASSIGN_OPERATOR_AMBIGUITY!>set += 2 to 2<!>
+}
+
+fun test3() {
+    var set = HashSet<Int>()
+    <!ASSIGN_OPERATOR_AMBIGUITY!>set -= 2<!>
+}
+
+fun test4() {
+    var list = mutableListOf(1)
+    <!ASSIGN_OPERATOR_AMBIGUITY!>list += 2<!>
+}
+
+fun test5() {
+    var map = mutableMapOf(1 to 1)
+    <!ASSIGN_OPERATOR_AMBIGUITY!>map += 2 to 2<!>
+}
+
+fun test6() {
+    var set = mutableSetOf(1)
+    <!ASSIGN_OPERATOR_AMBIGUITY!>set += 2<!>
+}