Optimize Imports shouldn't delete imports with unresolved parts

#KT-10512 Fixed

idea/testData/editor/optimizeImports/common/UnresolvedImport.dependency.kt

@@ -0,0 +1,3 @@
+package pack1
+
+class Example

idea/testData/editor/optimizeImports/common/UnresolvedImport.kt

@@ -0,0 +1,8 @@
+import pack1.Class4
+import pack1.Example
+import pack2.*
+import pack3.Ggd
+
+fun method(a: Class4) {
+    Example()
+}

idea/testData/editor/optimizeImports/common/UnresolvedImport.kt.after

@@ -0,0 +1,8 @@
+import pack1.Class4
+import pack1.Example
+import pack2.*
+import pack3.Ggd
+
+fun method(a: Class4) {
+    Example()
+}