fix(ivy): support injection flags for provider deps without new (#30216)

Previously, we were supporting injection flags for provider deps, but only
if they fit the format `new Optional()`. This commit fixes resolution of
provider deps to also support `Optional` (without the new). This keeps us
backwards compatible with what View Engine supported.

PR Close #30216

packages/core/test/acceptance/providers_spec.ts

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {Component, Directive, Inject, Injectable, InjectionToken, NgModule, forwardRef} from '@angular/core';
+import {Component, Directive, Inject, Injectable, InjectionToken, Injector, NgModule, Optional, forwardRef} from '@angular/core';
 import {TestBed, async, inject} from '@angular/core/testing';
 import {By} from '@angular/platform-browser';
 import {onlyInIvy} from '@angular/private/testing';
@@ -321,4 +321,25 @@ describe('providers', () => {
 
   });
 
+  describe('flags', () => {
+
+    class MyService {
+      constructor(public value: OtherService|null) {}
+    }
+
+    class OtherService {}
+
+    it('should support Optional flag in deps', () => {
+      const injector =
+          Injector.create([{provide: MyService, deps: [[new Optional(), OtherService]]}]);
+
+      expect(injector.get(MyService).value).toBe(null);
+    });
+
+    it('should support Optional flag in deps without instantiating it', () => {
+      const injector = Injector.create([{provide: MyService, deps: [[Optional, OtherService]]}]);
+
+      expect(injector.get(MyService).value).toBe(null);
+    });
+  });
 });