Java: Avoid duplicates for shadowed members in completion list for arguments of reflection calls. Simplify building the list of method names with PsiClass.getVisibleSignatures() (IDEA-167250)

java/java-tests/testData/codeInsight/completion/reflection/InheritedDeclaredMethod.java

@@ -7,9 +7,11 @@ class Main {
 class Test extends Parent {
   public void method(){}
   void method3(){}
+  private void method5(){}
 }
 
 class Parent {
   public void method2(){}
   void method4(){}
+  private void method6(){}
 }