Filter out dangerous CharSequences in Notification.

If an app mistakenly puts some Parcelable implementation of
CharSequence in here, Bundle will try to marshal the derived
class, which is going to be bad news when we try to unparcel
it in another process.

Additionally add a proper stack trace to unparceling
failures (otherwise you have no idea where the bad parcel
was being used).

Bug: 8725271
Change-Id: Ide19b986d65c7f47929cf2dde4e62b762c469fee