Fix search usages for invoke() with vararg parameter (KT-18479)

#KT-18479 Fixed

idea/testData/findUsages/kotlin/conventions/invokeWithVarArg.0.kt

@@ -0,0 +1,15 @@
+// PSI_ELEMENT: org.jetbrains.kotlin.psi.KtNamedFunction
+// OPTIONS: usages
+package pack
+
+class P {
+    operator fun <caret>invoke(vararg i: Int) = 1
+}
+
+fun f(p: P) {
+    p()
+    p(1, 2)
+    p(1)
+    p.invoke()
+    p.invoke(1, 2, 3)
+}

idea/testData/findUsages/kotlin/conventions/invokeWithVarArg.log

@@ -0,0 +1,7 @@
+Resolved p()
+Resolved p(1)
+Resolved p(1, 2)
+Searched references to pack.P
+Searched references to parameter p of pack.f(p: P) in non-Java files
+Used plain search of pack.P.invoke(vararg i: Int) in LocalSearchScope:
+    CLASS:P

idea/testData/findUsages/kotlin/conventions/invokeWithVarArg.results.txt

@@ -0,0 +1,5 @@
+Function call 13 p.invoke()
+Function call 14 p.invoke(1, 2, 3)
+Implicit 'invoke' 10 p()
+Implicit 'invoke' 11 p(1, 2)
+Implicit 'invoke' 12 p(1)