Make visibility of an issue or merge request easier to accertain

I recently commented on an issue in a project which I did not realize was not public, and this made me realize that there isn't an easy way to see whether a project is set as "private" or "internal" without visiting the project's "details" or "settings" pages. I think this would be good to display on all pages where it might be useful information.

Currently we have the ability to mark issues as "confidential" and they are made visually distinct with the eye-slash icon appearing in the header and a banner above the comment form indicating that your comment will not be made public.

in header	in comment form

This is really useful, and I think it may also be useful to use something like this (but perhaps a little more subtle) for an issue/merge request which might not be made public for other reasons, such as when you are in a "private" project or an "internal" group.

Here are some quick mockups I threw together:

In navigation breadcrumbs

We could also show the project group's (and parent groups) visibility here, but I'd suggest we only show the prevailing visibility for the project here, to reduce confusion and visual noise.

Next to project icon

I think this may get annoying if we put it in the way of the project icon on all pages

In issue/mr header

Here we'd have to add it to specific pages individually, rather than adding it once to a navigation component that will be visible everywhere, but I like the placement here.