Add multi-file completion handler tests for FIR code completion

This is a temporary (and dirty) solution to start using those tests as
fast as possible. We certainly need to refactor them so they can be
generated from the testData

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

@@ -1,3 +1,4 @@
+// FIR_COMPARISON
 fun foo() {
     KtCla<caret>
 }

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

@@ -1,5 +1,6 @@
 import pack.KtClass
 
+// FIR_COMPARISON
 fun foo() {
     KtClass<caret>
 }

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

@@ -1,3 +1,4 @@
+// FIR_COMPARISON
 fun foo() {
     val s = "fo<caret>something"
 }

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

@@ -1,3 +1,4 @@
+// FIR_COMPARISON
 fun foo() {
     val s = "foo.txtsomething"
 }

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

@@ -1,3 +1,4 @@
+// FIR_COMPARISON
 fun foo() {
     val s = "fo<caret>something"
 }

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

@@ -1,3 +1,4 @@
+// FIR_COMPARISON
 fun foo() {
     val s = "foo.txt"
 }

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

@@ -1,3 +1,4 @@
+// FIR_COMPARISON
 object XXX {
     fun authorize(handler: String.() -> Unit) { }
 }

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

@@ -1,5 +1,6 @@
 import ppp.globalFun
 
+// FIR_COMPARISON
 object XXX {
     fun authorize(handler: String.() -> Unit) { }
 }

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

@@ -1,3 +1,4 @@
+// FIR_COMPARISON
 package some
 
 import test.SomeTestObject

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

@@ -1,3 +1,4 @@
+// FIR_COMPARISON
 package some
 
 import test.SomeTestObject

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

@@ -1,3 +1,4 @@
+// FIR_COMPARISON
 package classimporttest
 
 fun test() {

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

@@ -1,3 +1,4 @@
+// FIR_COMPARISON
 package classimporttest
 
 import forimport.TTTest

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

@@ -1,3 +1,4 @@
+// FIR_COMPARISON
 package a
 
 class Goo {

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

@@ -1,3 +1,4 @@
+// FIR_COMPARISON
 package a
 
 import a.b.foo