Enhancement: Improve a11y in the files sidebar peoples & shares section

We've did several improvements to enhance the accessibility on the files sidebar:
- Gave `role="presentation" to the collaborator avatar
- Refactored `<span>` and `<div>` tags into `<p>` tags and unified translations a bit
- Enhanced hints in the collaborator quick action buttons with collaborator name
- Hide private links if the capability is not enabled
- Set avatar-images to `:aria-hidden="true"` since they're only visual elements and can be hidden from screenreaders
- Changed `<section>` wrapper around private link shares
- Removed `<section>` wrapper around public link shares
- Removed `<section>` wrapper around collaborators
- Added screenreader-only explain texts regarding collaborator/share ownership
- Added aria-label for share receiver section
- Worked on unifying the way we handle translations: Focus on v-translate and $gettext()
- Turn tags into `<ul> & <li>` list, add aria-labelledby to both tag list and resharer tag list
- Translated "Open with $appName" for sidebar quick actions

https://github.com/owncloud/web/pull/5034
https://github.com/owncloud/web/pull/5043
https://github.com/owncloud/web/pull/5121
