Add tag-based caching to notifications and activity stream views

Problem/Motivation

There are notification and activity stream views without caching enabled:

• modules/social_features/social_activity/config/install/views.view.activity_stream_profile.yml
• modules/social_features/social_activity/config/install/views.view.activity_stream_notifications.yml
• modules/social_features/social_activity/config/install/views.view.activity_stream_group.yml

Proposed resolution

It should be fairly safe to enable tag-based caching.