Smart completion: no more duplicates among type instantiation items

idea/testData/completion/handlers/smart/MergeTail1.kt

@@ -0,0 +1,8 @@
+class C{}
+
+fun foo(c: C){}
+fun foo(c: C, i: Int){}
+
+fun foo() {
+    foo(<caret>
+}

idea/testData/completion/handlers/smart/MergeTail1.kt.after

@@ -0,0 +1,8 @@
+class C{}
+
+fun foo(c: C){}
+fun foo(c: C, i: Int){}
+
+fun foo() {
+    foo(C()<caret>
+}

idea/testData/completion/handlers/smart/MergeTail2.kt

@@ -0,0 +1,8 @@
+class C{}
+
+fun foo(c: C){}
+fun foo(c: C?, i: Int){}
+
+fun foo() {
+    foo(<caret>
+}

idea/testData/completion/handlers/smart/MergeTail2.kt.after

@@ -0,0 +1,8 @@
+class C{}
+
+fun foo(c: C){}
+fun foo(c: C?, i: Int){}
+
+fun foo() {
+    foo(C()<caret>
+}