Imports on paste tests: generate result if does not exist and use default target file text

idea/testData/copyPaste/conversion/AddImportsButNoConversion.expected.kt

@@ -1,3 +1,3 @@
 import java.io.File
 
-fun foo(): List<File><caret>
+fun foo(): List<File>

idea/testData/copyPaste/conversion/AddImportsButNoConversion2.expected.kt

@@ -1,5 +1,5 @@
 import java.io.File
 
 fun foo() {
-    list.add(File.separatorChar)<caret>
+    list.add(File.separatorChar)
 }

idea/testData/copyPaste/conversion/AddImportsClassInSamePackage.expected.kt

@@ -1,5 +1,5 @@
 import ppp.Dependency
 
 fun f() {
-    return Dependency.FIELD<caret>
+    return Dependency.FIELD
 }

idea/testData/copyPaste/conversion/AddImportsDummyConflict.expected.kt

@@ -1,5 +1,5 @@
 import ppp.dummy0
 
 fun f() {
-    return dummy0()<caret>
+    return dummy0()
 }