The Events Calendar - Event Tickets Plus 5.10.1

* Version - Event Tickets Plus 5.7.1 is only compatible with Event Tickets 5.6.1 and higher.
* Fix - Lock our container usage(s) to the new Service_Provider contract in tribe-common. This prevents conflicts and potential fatals with other plugins that use a di52 container.

* Fix - Resolved issues with Attendee Registration not being bound correctly on loading. [ET-1771]

* Feature - Introduction of Tickets Emails, the new and improved solution for managing Event Tickets related emails.
* Tweak - Changed views: `v2/emails/template-parts/body/ticket/ar-fields`, `v2/emails/template-parts/body/ticket/ar-fields/data`, `v2/emails/template-parts/body/ticket/ar-fields/key`, `v2/emails/template-parts/body/ticket/ar-fields/value`, `v2/emails/template-parts/body/ticket/qr-image`, `v2/emails/template-parts/header/head/ar-styles`
* Language - 9 new strings added, 18 updated, 3 fuzzied, and 2 obsoleted