Escaping of keyword names in completion (more tests to be added)

idea/testData/completion/handlers/KeywordClassName.kt

@@ -0,0 +1,5 @@
+package test
+
+class `class`
+
+fun foo(p: <caret>)

idea/testData/completion/handlers/KeywordClassName.kt.after

@@ -0,0 +1,5 @@
+package test
+
+class `class`
+
+fun foo(p: `class`<caret>)

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

@@ -0,0 +1,5 @@
+package first
+
+fun foo() {
+    "".pack<caret>
+}

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

@@ -0,0 +1,3 @@
+package second
+
+fun String.`package`() { }

idea/testData/completion/handlers/multifile/KeywordExtensionFunctionName.kt.after

@@ -0,0 +1,7 @@
+package first
+
+import second.`package`
+
+fun foo() {
+    "".`package`()
+}