Email Notifications should display the events in the order they were performed

Preconditions: Mail Sending for the instance should be configured from Administration.

Steps to reproduce

1. Edit xwiki.properties and set notifications.emails.live.graceTime = 1 to enable the sending of e-mails after 1 minute
2. Login as an user (e.g. U1) which has an email set in his profile
3. Click on Notifications Bell and set all Watch toggles to ON
4. Go to Notifications Settings
5. Set "Email Frequency" to Live
6. Login as Admin or other user
7. Perform the following actions in order: create a page, edit it, delete it, comment in another page, mention the user U1 in another page
8. Check the order of events in the user's U1 received emails

Expected results

The email received displays notifications events in the order they were performed (last finished event on the top of the list).

Actual results

The order of the events from the notifications mail doesn't correspond to the order the events were performed.

The same issue reproduces if the "Email Frequency" is set to 'Hourly'.