chore: Migrate Popover Dropdown component

[arnolicious]

As mentioned over here: immich-app/immich#18570

This moves the "Popover Dropdown" component from the main project to the ui lib, and refactors it to use the Popover from bits-ui. This fixes some clipping/overflow issues when using the dropdown inside a modal (specifically the SlideshowSettingsModal)

Screenshots

[danieldietzler]

LGTM!

[danieldietzler]

Screenshots in the PR description would be a nice addition, especially because we don't get a preview env :)

[arnolicious]

I've now refactored the component to have a more aligned interface like the Select component, alongside with allowing for a custom trigger element to be passed in.

With that custom trigger, I could also now remove all the button props (color, shape, variant, size), should I?

[danieldietzler]

This looks pretty good!

[danieldietzler]

I would probably do this in JS land with {value?.label || placeholder}. That's definitely exclusively personal preference though

[arnolicious]

oh yeah agreed, that's a remnant of what I had there before

[danieldietzler]

I could also now remove all the button props (color, shape, variant, size), should I?

I don't think so. That's much more convenient if you only want to change a single thing.