Ensure group summary (and any notifications added directly by NMS) have the correct token

All notifications must have the same token so that their serialization works as intended.

Bug: 328254922
Bug: 305695605
Bug: 346360609
Flag: android.app.secure_allowlist_token
Test: atest NotificationManagerServiceTest
(cherry picked from commit c18c614a)
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:faba96efff401d77243a3f257fb12512a8efe379)
Merged-In: I26784a729506169b3fe8481094cc4f5ab7b8a92b
Change-Id: I26784a729506169b3fe8481094cc4f5ab7b8a92b