KT-10770 IDEA cannot keep import if a type is only referenced by kdoc.

#KT-10770 Fixed

idea/testData/editor/optimizeImports/KDocReference.kt

@@ -0,0 +1,12 @@
+// RUNTIME
+import kotlin.concurrent.fixedRateTimer
+import kotlin.concurrent.read
+import java.util.ArrayList
+
+/**
+ * Reference to [ArrayList]
+ * Reference to [fixedRateTimer]
+ * Reference to [kotlin.concurrent.read]
+ */
+fun foo() {
+}

idea/testData/editor/optimizeImports/KDocReference.kt.after

@@ -0,0 +1,11 @@
+// RUNTIME
+import java.util.ArrayList
+import kotlin.concurrent.fixedRateTimer
+
+/**
+ * Reference to [ArrayList]
+ * Reference to [fixedRateTimer]
+ * Reference to [kotlin.concurrent.read]
+ */
+fun foo() {
+}

idea/testData/inspections/unusedImport/inspectionData/expected.xml

@@ -88,4 +88,13 @@
         <problem_class severity="WARNING" attribute_key="NOT_USED_ELEMENT_ATTRIBUTES">Unused import directive</problem_class>
         <description>Unused import directive</description>
     </problem>
+
+    <problem>
+        <file>kDocReferences.kt</file>
+        <line>2</line>
+        <module>light_idea_test_case</module>
+        <entry_point TYPE="file" FQNAME="kDocReferences.kt" />
+        <problem_class severity="WARNING" attribute_key="NOT_USED_ELEMENT_ATTRIBUTES">Unused import directive</problem_class>
+        <description>Unused import directive</description>
+    </problem>
 </problems>

idea/testData/inspections/unusedImport/kDocReferences.kt

@@ -0,0 +1,11 @@
+import kotlin.concurrent.fixedRateTimer
+import kotlin.concurrent.read
+import java.util.ArrayList
+
+/**
+ * Reference to [ArrayList]
+ * Reference to [fixedRateTimer]
+ * Reference to [kotlin.concurrent.read]
+ */
+fun foo() {
+}