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/DeclaredMethod_after.java

@@ -23,6 +23,7 @@ class Test {
   public void method(){}
   public void method2(A a, B b){}
   void method1(){}
+  private void method0(C c) {}
 }
 
 class A {}