[PM-2282] Make feature flags type safe (#8612)

Refactors the feature flags in ConfigService to be type safe. It also moves the default value to a centralized location rather than the caller defining it. This ensures consistency across the various places they are used.

apps/web/src/app/vault/components/collection-dialog/collection-dialog.component.ts

@@ -76,7 +76,7 @@ export enum CollectionDialogAction {
 })
 export class CollectionDialogComponent implements OnInit, OnDestroy {
   protected flexibleCollectionsV1Enabled$ = this.configService
-    .getFeatureFlag$(FeatureFlag.FlexibleCollectionsV1, false)
+    .getFeatureFlag$(FeatureFlag.FlexibleCollectionsV1)
     .pipe(first());
 
   private destroy$ = new Subject<void>();