patch 8.2.3996: Vim9: type checking lacks information about declared type

Problem:    Vim9: type checking for list and dict lacks information about
            declared type.
Solution:   Add dv_decl_type and lv_decl_type.  Refactor the type stack to
            store two types in each entry.
diff --git a/src/testdir/test_vim9_builtin.vim b/src/testdir/test_vim9_builtin.vim
index 7b83510..d957c15 100644
--- a/src/testdir/test_vim9_builtin.vim
+++ b/src/testdir/test_vim9_builtin.vim
@@ -982,26 +982,22 @@
   END
   CheckDefAndScriptSuccess(lines)
 
-  # FIXME: this should not fail when compiled
   lines =<< trim END
-      vim9script
       assert_equal([1, 2, "x"], extend([1, 2], ["x"]))
       assert_equal([1, "b", 1], extend([1], ["b", 1]))
+
+      assert_equal({a: 1, b: "x"}, extend({a: 1}, {b: "x"}))
   END
-  CheckScriptSuccess(lines)
+  CheckDefAndScriptSuccess(lines)
 
   CheckDefAndScriptFailure(['extend("a", 1)'], ['E1013: Argument 1: type mismatch, expected list<any> but got string', 'E712: Argument of extend() must be a List or Dictionary'])
-  CheckDefAndScriptFailure(['extend([1, 2], 3)'], ['E1013: Argument 2: type mismatch, expected list<number> but got number', 'E712: Argument of extend() must be a List or Dictionary'])
+  CheckDefAndScriptFailure(['extend([1, 2], 3)'], ['E1013: Argument 2: type mismatch, expected list<any> but got number', 'E712: Argument of extend() must be a List or Dictionary'])
   CheckDefAndScriptFailure(['var ll = [1, 2]', 'extend(ll, ["x"])'], ['E1013: Argument 2: type mismatch, expected list<number> but got list<string>', 'E1013: Argument 2: type mismatch, expected list<number> but got list<string>'])
   CheckDefFailure(['extend([1, 2], [3], "x")'], 'E1013: Argument 3: type mismatch, expected number but got string')
 
-  CheckDefFailure(['extend({a: 1}, 42)'], 'E1013: Argument 2: type mismatch, expected dict<number> but got number')
-  CheckDefFailure(['extend({a: 1}, {b: "x"})'], 'E1013: Argument 2: type mismatch, expected dict<number> but got dict<string>')
+  CheckDefFailure(['extend({a: 1}, 42)'], 'E1013: Argument 2: type mismatch, expected dict<any> but got number')
   CheckDefFailure(['extend({a: 1}, {b: 2}, 1)'], 'E1013: Argument 3: type mismatch, expected string but got number')
 
-  CheckDefFailure(['extend([1], ["b"])'], 'E1013: Argument 2: type mismatch, expected list<number> but got list<string>')
-  CheckDefExecFailure(['extend([1], ["b", 1])'], 'E1013: Argument 2: type mismatch, expected list<number> but got list<any>')
-
   CheckScriptFailure(['vim9script', 'var l = [1]', 'extend(l, ["b", 1])'], 'E1013: Argument 2: type mismatch, expected list<number> but got list<any> in extend()')
 enddef