refactor(core): Privately export SchedulingMode enum (#55100)

Expose enum for early testers so they don't have to awkwardly put `0`
for Hybrid mode.

PR Close #55100

packages/core/src/core_private_export.ts

@@ -12,6 +12,7 @@ export {IMAGE_CONFIG as ɵIMAGE_CONFIG, IMAGE_CONFIG_DEFAULTS as ɵIMAGE_CONFIG_
 export {internalCreateApplication as ɵinternalCreateApplication} from './application/create_application';
 export {defaultIterableDiffers as ɵdefaultIterableDiffers, defaultKeyValueDiffers as ɵdefaultKeyValueDiffers} from './change_detection/change_detection';
 export {getEnsureDirtyViewsAreAlwaysReachable as ɵgetEnsureDirtyViewsAreAlwaysReachable, setEnsureDirtyViewsAreAlwaysReachable as ɵsetEnsureDirtyViewsAreAlwaysReachable} from './change_detection/flags';
+export {SchedulingMode as ɵSchedulingMode} from './change_detection/scheduling/ng_zone_scheduling';
 export {ChangeDetectionScheduler as ɵChangeDetectionScheduler, ZONELESS_ENABLED as ɵZONELESS_ENABLED} from './change_detection/scheduling/zoneless_scheduling';
 export {provideZonelessChangeDetection as ɵprovideZonelessChangeDetection} from './change_detection/scheduling/zoneless_scheduling_impl';
 export {Console as ɵConsole} from './console';