Vue Popover - Reduce technical footprint

What / Why

Follow up from conversation here: !154955 (comment 1932238035)

We have a new shared component VuePopover that allows for a lightweight way to include GlPopover in HAML files without the need to create new Vue applications/code.

However, the current implementation creates a new Vue instance for every popover. This is a bit inefficient and rather it would be nice to create one Vue instance that is able to handle/manage multiple popovers and their triggers on a single page through on Vue instance.

Proposal

• Refactor vue_popovers.js to be one Vue instance rather than multiple
• This Vue instance is able to scan the DOM for all instances of .js-vue-popover and manage them all from that one Vue instance rather than multiple.

cc/ @pslaughter