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/InheritedDeclaredField.java

@@ -7,9 +7,11 @@ class Main {
 class Test extends Parent {
   public int num;
   int num3;
+  private int num5;
 }
 
 class Parent {
   public int num2;
   int num4;
+  private int num6;
 }