Add the test case for begin/private destinations

for the "go to definition" request.

Author: reznikmm

testsuite/ada_lsp/definition_begin/main.adb

@@ -0,0 +1,86 @@
+procedure Main is
+   package Pkg is
+      X : Integer;
+   private
+      function Y return Integer;
+   end Pkg;
+
+   package body Pkg is
+      Z : Integer;
+
+      function Y return Integer is
+      begin
+         return (Z);
+      end Y;
+
+   begin
+      Z := 0;
+   end Pkg;
+
+   protected type Pr_Type is
+      procedure Proc;
+   private
+      procedure Priv;
+   end Pr_Type;
+
+   protected body Pr_Type is
+      procedure Proc is
+      begin
+         Priv;
+      end Proc;
+
+      procedure Priv is
+      begin
+         null;
+      end Priv;
+   end Pr_Type;
+
+   protected Pr_Obj is
+      procedure Proc;
+   private
+      procedure Priv;
+   end Pr_Obj;
+
+   protected body Pr_Obj is
+      procedure Proc is
+      begin
+         Priv;
+      end Proc;
+
+      procedure Priv is
+      begin
+         null;
+      end Priv;
+   end Pr_Obj;
+
+   task type Task_Type is
+      pragma Page;
+   private
+      entry Entr;
+   end Task_Type;
+
+   task body Task_Type is
+      X : Integer;
+   begin
+      loop
+         accept Entr;
+      end loop;
+   end Task_Type;
+
+   task Task_Obj is
+      pragma Page;
+   private
+      entry Entr;
+   end Task_Obj;
+
+   task body Task_Obj is
+      X : Integer;
+   begin
+      loop
+         accept Entr;
+      end loop;
+   end Task_Obj;
+
+begin
+   null;
+end Main;