eventcart: on EventInfo, show checkout/viewcart buttons

[mlutfy]

Overview

When using the "Event Cart" feature, display buttons to "View Cart" and "Checkout" (if there are items in the cart).

I have seen a few reports that the "view cart" message was often not obvious to users, and if you miss it, then there is no way to find your cart.

Before

After

Comments

An alternative could be to display those buttons as plain links:

I took some inspiration from the boxoffice extension: https://civicrm.org/extensions/boxoffice

[civibot]

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