Replace Bootstrap plugins

[matthew-white]

We use several Bootstrap 3 plugins. It'd be nice to remove them, for a few reasons:

• The plugins require jQuery, which is one of our heaviest dependencies. We have removed all other uses of jQuery.
• The plugins don't always play well with Vue. For example, our Popover component has significant limitations due to its use of the Bootstrap popover plugin.
• Bootstrap 3 has reached EOL. I doubt that it'd be simple to migrate to Bootstrap 4 or 5. We also don't really want to continue using Bootstrap from a design perspective.

These are the Bootstrap plugins that we currently use:

• collapse
  • This is just needed for the Navbar component I think.
  • Possibly it won't be needed anymore once we implement Set minimum width #785
• popover + tooltip
  • These are needed for the Popover component.
  • We use Floating UI for our tooltips, and I'd like to replace these plugins with Floating UI.
• modal
  • This is needed for the Modal component.
  • I doubt this plugin is doing that much, so I think we should just implement the modal functionality ourselves. Our Modal component does a lot beyond what the plugin does, so I think it'd be better if we could control everything related to it rather than using an external component.
• dropdown
  • Unlike some of the other plugins, this isn't used in a single generic component. Instead, it's used throughout Frontend, mostly via data attributes.
  • I think the main thing that the plugin's doing is positioning the dropdown menu once the dropdown has been opened. We could probably use Floating UI for that.
• transition
  • This is imported, but I'm actually not sure that we use it for anything.