fix #29182, generate top level const fields lazily

pkg/dev_compiler/test/codegen_expected/closure.js

 export const closure = Object.create(null);
 import { core, js, dart, dartx } from 'dart_sdk';
 let dynamic__Toint = () => (dynamic__Toint = dart.constFn(dart.functionType(core.int, [dart.dynamic], [dart.dynamic])))();
 let dynamic__Todynamic = () => (dynamic__Todynamic = dart.constFn(dart.functionType(dart.dynamic, [dart.dynamic], {y: core.String, z: dart.dynamic})))();
 let StringToList = () => (StringToList = dart.constFn(dart.functionType(core.List, [core.String])))();
 let ListOfint = () => (ListOfint = dart.constFn(core.List$(core.int)))();
 let dynamicTodynamic = () => (dynamicTodynamic = dart.constFn(dart.functionType(dart.dynamic, [dart.dynamic])))();
 let FnToListOfint = () => (FnToListOfint = dart.constFn(dart.functionType(ListOfint(), [dynamicTodynamic()])))();
 let MapOfMap$Map = () => (MapOfMap$Map = dart.constFn(core.Map$(core.Map, core.Map)))();
 let Foo = () => (Foo = dart.constFn(closure.Foo$()))();
@@ skipping 97 matching lines @@
       nullary_method: dart.definiteFunctionType(dart.dynamic, []),
       function_params: dart.definiteFunctionType(dart.dynamic, [dynamic__Toint(), dynamic__Todynamic(), closure.Callback]),
       run: dart.definiteFunctionType(dart.dynamic, [core.List, core.String, StringToList(), FnToListOfint()], {h: MapOfMap$Map()})
     }),
     statics: () => ({named_params: dart.definiteFunctionType(dart.dynamic, [dart.dynamic], {b: dart.dynamic, c: core.int})}),
     names: ['named_params']
   });
   return Foo;
 });
 closure.Foo = Foo();
-/** @final {string} */
-closure.Foo.some_static_constant = "abc";
-/** @final {string} */
-closure.Foo.some_static_final = "abc";
-/** @type {string} */
-closure.Foo.some_static_var = "abc";
+dart.defineLazy(closure.Foo, {
+  get some_static_constant() {
+    return "abc";
+  },
+  get some_static_final() {
+    return "abc";
+  },
+  get some_static_var() {
+    return "abc";
+  },
+  set some_static_var(_) {}
+});
 closure.Bar = class Bar extends core.Object {};
 closure.Baz = class Baz extends dart.mixin(closure.Foo$(core.int), closure.Bar) {
   new(i: number) {
     super.new(i, 123);
   }
 };
 dart.addSimpleTypeTests(closure.Baz);
 closure.main = function(args): void {
 };
 dart.fn(closure.main, dynamicTovoid());
 dart.defineLazy(closure, {
   get closure() {
     return dart.fn((): core.Null => {
       return;
     }, VoidToNull());
   },
-  set closure(_) {}
+  set closure(_) {},
+  get some_top_level_constant() {
+    return "abc";
+  },
+  get some_top_level_final() {
+    return "abc";
+  },
+  get some_top_level_var() {
+    return "abc";
+  },
+  set some_top_level_var(_) {}
 });
-/** @final {string} */
-closure.some_top_level_constant = "abc";
-/** @final {string} */
-closure.some_top_level_final = "abc";
-/** @type {string} */
-closure.some_top_level_var = "abc";
 dart.trackLibraries("closure", {"closure.dart": closure}, null);