Include private events on the calendar if the current user has the capability to view them

[Pebblo]

Problem this Pull Request solves

See: https://events.codebasehq.com/projects/event-espresso/tickets/9788 And: https://eventespresso.com/topic/private-events-in-calendar/

How has this been tested

Set an event to be private.

View the calendar whilst not logged into the site, that event should not be viewable.

View the calendar whilst logged in as a subscriber, again, the event should not be viewable.

Update your user account to have the ee_read_private_events events cap, the event should now be viewable.

Checklist

• [x] I have read the documentation relating to systems affected by this pull request, see https://github.com/eventespresso/event-espresso-core/tree/master/docs
• [x] User input is adequately validated and sanitized
• [x] all publicly displayed strings are internationalized (usually using esc_html__(), see https://codex.wordpress.org/I18n_for_WordPress_Developers)
• [x] My code is tested.
• [x] My code follows the Event Espresso code style.
• [x] My code has proper inline documentation.

[sethshoultes]

This is working for me as outlined in the testing notes

[sethshoultes]

@Pebblo do you want further testing on this or do you think it's okay for release?

[Pebblo]

Thanks Seth. I think this can be released as is.