Remove support for the DeferredLibrary annotation and remove tests of it

tests/language/language.status

 # Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 # This directory contains tests that are intended to show the
 # current state of the language.
 
 [ $compiler == none ]
 mixin_super_constructor_named_test: Fail # Issue 12631
 mixin_super_constructor_positionals_test: Fail # Issue 12631
 built_in_identifier_prefix_test: Fail # Issue 6970
 
 # These bugs refer currently ongoing language discussions.
 constructor_initializer_test/none: Fail # Issue 12633
 constructor5_test: Fail # Issue 6422
 constructor6_test: Fail # Issue 6422
 closure_in_initializer_test: Fail # Issue 6422
 
 # Regular bugs which should be fixed.
 duplicate_export_negative_test: Fail # Issue 6134
 mixin_forwarding_constructor2_test: Fail # Issue 13641
 
-# These test use the old syntax, and will be phased out.
-deferred_constraints_constants_old_syntax_test/reference1: Fail, Ok
-deferred_constraints_constants_old_syntax_test/reference2: Fail, Ok
-deferred_constraints_constants_old_syntax_test/metadata1: Fail, Ok
-deferred_constraints_constants_old_syntax_test/metadata2: Fail, Ok
-deferred_constraints_constants_old_syntax_test/metadata3: Fail, Ok
-deferred_constraints_constants_old_syntax_test/default_argument1: Fail, Ok
-deferred_constraints_constants_old_syntax_test/default_argument2: Fail, Ok
-deferred_constraints_constants_old_syntax_test/constructor1: Fail, Ok
-deferred_constraints_constants_old_syntax_test/constructor2: Fail, Ok
 
 [ $runtime != vm ]
 # Async/await is currently only supported by the vm.
 async_test/*: Skip
 async_control_structures_test: Skip
 await_test: Skip
 await_future_test: Skip
 await_backwards_compatibility_test/*: Skip
 
 [ $compiler == dart2dart]
@@ skipping 10 matching lines @@
 deferred_constraints_constants_test/*: Fail, Pass # Issue 17523
 deferred_shadow_load_library_test: Fail # Issue 17523
 deferred_closurize_load_library_test: Fail  # Issue 17523
 deferred_inlined_test: Fail  # Issue 17523
 deferred_optimized_test: Fail  # Issue 17523
 
 override_inheritance_mixed_test/08: Fail # Issue 18124
 override_inheritance_mixed_test/09: Fail # Issue 18124
 
 [ $compiler == none || $compiler == dart2dart]
-# These test use the old syntax, and will be phased out.
-deferred_constraints_type_annotation_old_syntax_test/as_operation: Fail, Ok
-deferred_constraints_type_annotation_old_syntax_test/is_check: Fail, Ok
-deferred_constraints_type_annotation_old_syntax_test/catch_check: Fail, Ok
-deferred_constraints_type_annotation_old_syntax_test/new_before_load: Fail, Ok
-
 # Non-contractive types are not supported in the vm.
 cyclic_type_test/02: Fail, OK
 cyclic_type_test/04: Fail, OK
 cyclic_type2_test: Fail, OK
 least_upper_bound_expansive_test/*: Fail, OK
 
-[ ($compiler == none || $compiler == dart2dart) && $checked ]
-# Issue 17521, 17523
-# Dart2dart does not support deferred loading.
-deferred_constraints_type_annotation_old_syntax_test/type_annotation1: Fail
-deferred_constraints_type_annotation_old_syntax_test/type_annotation_generic1: Fail
-deferred_constraints_type_annotation_old_syntax_test/type_annotation_generic4: Fail
-
-[ $compiler == none || $compiler == dartanalyzer || $compiler == dart2analyzer ]
-# Issue 17521, 17522
-deferred_no_prefix_old_syntax_test/01: Fail
-deferred_duplicate_prefix1_old_syntax_test/01: Fail
-deferred_duplicate_prefix2_old_syntax_test/01: Fail
-deferred_duplicate_prefix3_old_syntax_test/01: Fail
-
 [ $compiler == none && $runtime == vm ]
 class_keyword_test/02: MissingCompileTimeError # Issue 13627
 
 unicode_bom_test: Fail # Issue 16067
 
 [ $compiler == none && $checked ]
 type_variable_bounds4_test/01: Fail # Issue 14006
 
 [ $compiler == none && $unchecked ]
 # Only checked mode reports an error on type assignment
@@ skipping 42 matching lines @@
 
 [ $compiler == none && $runtime == vm && $arch == mips && $mode == debug ]
 stack_overflow_test: Skip # Crashes. Issue 17440.
 stack_overflow_stacktrace_test: Skip # Crashes. Issue 17440.
 large_class_declaration_test: Skip # Times out. Issue 20352
 
 [ $compiler == none && ($runtime == dartium || $runtime == drt || $runtime == ContentShellOnAndroid) && $mode == debug ]
 large_class_declaration_test: Skip # Times out. Issue 20352