fix(core): export inject() from @angular/core (#22389)

inject() supports the ngInjectableDef-based configuration of the injector
(otherwise known as tree-shakeable services). It was missing from the
exported API of @angular/core, this PR adds it.

The test added here is correct in theory, but may pass accidentally due
to the decorator side-effect replacing the inject() call at runtime. An
upcoming compiler PR will strip reified decorators from the output
entirely.

Fixes #22388

PR Close #22389

packages/compiler-cli/integrationtest/bazel/injectable_def/app/test/app_spec.ts

@@ -9,6 +9,7 @@
 import {enableProdMode} from '@angular/core';
 import {renderModuleFactory} from '@angular/platform-server';
 import {BasicAppModuleNgFactory} from 'app_built/src/basic.ngfactory';
+import {DepAppModuleNgFactory} from 'app_built/src/dep.ngfactory';
 import {HierarchyAppModuleNgFactory} from 'app_built/src/hierarchy.ngfactory';
 import {RootAppModuleNgFactory} from 'app_built/src/root.ngfactory';
 import {SelfAppModuleNgFactory} from 'app_built/src/self.ngfactory';
@@ -66,4 +67,14 @@ describe('ngInjectableDef Bazel Integration', () => {
       done();
     });
   });
+
+  it('can inject dependencies', done => {
+    renderModuleFactory(DepAppModuleNgFactory, {
+      document: '<dep-app></dep-app>',
+      url: '/',
+    }).then(html => {
+      expect(html).toMatch(/>true<\//);
+      done();
+    });
+  });
 });