feat(core): Introduce TestBed.inject to replace TestBed.get (#32200)

TestBed.get is not type safe, fixing it would be a massive breaking
change. The Angular team has proposed replacing it with TestBed.inject
and deprecate TestBed.get.

Deprecation from TestBed.get will come as a separate commit.

Issue #26491
Fixes #29905

BREAKING CHANGE: Injector.get now accepts abstract classes to return
type-safe values. Previous implementation returned `any` through the
deprecated implementation.

PR Close #32200

packages/core/test/render3/view_container_ref_spec.ts

@@ -299,7 +299,7 @@ describe('ViewContainerRef', () => {
              const changeDetector = ref.injector.get(ChangeDetectorRef);
              changeDetector.detectChanges();
              expect(dynamicComp.doCheckCount).toEqual(1);
-             expect(changeDetector.context).toEqual(dynamicComp);
+             expect((changeDetector as any).context).toEqual(dynamicComp);
            });
 
         it('should not throw when destroying a reattached component', () => {