KT-8979 Completion of non-imported extension with "!" character corrupts code

#KT-8979 Fixed

idea/idea-completion/testData/handlers/multifile/ExclCharInsertImport-1.kt

@@ -0,0 +1,8 @@
+package qqqq
+
+import a
+import b
+
+fun foo() {
+    "".isX<caret>
+}

idea/idea-completion/testData/handlers/multifile/ExclCharInsertImport-2.kt

@@ -0,0 +1,4 @@
+package foo
+
+val String.isXXX: Boolean
+    get() = true

idea/idea-completion/testData/handlers/multifile/ExclCharInsertImport.kt.after

@@ -0,0 +1,9 @@
+package qqqq
+
+import a
+import b
+import foo.isXXX
+
+fun foo() {
+    !"".isXXX<caret>
+}