[native] Add filtering entitlement to Notification Service Extension

Test Plan:
Confirmed that Xcode is able to load the refreshed Provisioning Profile for the Notification Service Extension, and that the relevant entitlement is listed:

In order to test whether the entitlement works as expected complete the following steps:

1. Modify NotificationService.mm as here: https://gist.github.com/marcinwasowicz/193fb4916b277537a4b7f9e88a456e06
2. Unblock this flag on keyserver side: https://github.com/CommE2E/comm/blob/master/keyserver/src/push/send.js#L509
3. Ensure that notification are not displayed even though app is given suitable permission.

This test plan might need to be executed on physical device.

Reviewers: marcin, atul

Reviewed By: marcin

Subscribers: tomek, marcin

Differential Revision: https://phab.comm.dev/D6847