KT-1850 Fixed: Redundant imports are not removed when classes are used only by FQ name

OptimizeImportsMultiFileTest added

idea/testData/editor/optimizeImports/multifile/KotlinPackage/KotlinPackage_after.kt

@@ -0,0 +1,3 @@
+import test1.test2
+
+val s: test2.test3.Class1? = null

idea/testData/editor/optimizeImports/multifile/KotlinPackage/kotlinClass.kt

@@ -0,0 +1,4 @@
+package test1.test2.test3
+
+public class Class1 {
+}

idea/testData/editor/optimizeImports/multifile/KotlinPackage/main.kt

@@ -0,0 +1,6 @@
+import test1
+import test1.test2
+import test1.test2.test3
+import test1.test2.test3.Class1
+
+val s: test2.test3.Class1? = null