refactor(ivy): create Injector interface; remove dependency on Ivy (#28066)

This change is a prerequasity for a later change which will turn the
'di' into its own bazel package. In order to do that we have to:
- have `Injector` type be importable by Ivy. This means that we need
  to create `Injector` as a pure type in `interface` folder which is
  already a bazel package which Ivy can depend on.
- Remove the dependency of `class Injector` on Ivy so that it can be
  compiled in isolation. We do that by using `-1` as special value for
  `__NG_ELEMENT_ID__` which tells the Ivy `NodeInjector` than
  `Injector` is being requested.

PR Close #28066

packages/core/src/di/scope.ts

@@ -6,7 +6,6 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {Type} from '../interface/type';
 import {InjectionToken} from './injection_token';