Block Editor: LinkControl: Remove Popover-associated styling

[aduth]

Previously: #18061 (comment)

LinkControl is intended to be used as a standalone form field, much like other *Control input control components. As such, it should make no assumptions about the context in which it is rendered. Currently, there is styling applied to the LinkControl component which assumes that it would be rendered to appear within a popover modal. This should be removed from the underlying component.

Ideally, a generic component like this can "just work" when rendered within a popover. If popover styling is insufficient, it should be considered whether the default popover styling (e.g. padding) is adequate for intended usages. The idea here is: We should avoid the idea that these sorts of components are special and instead aim to have a good set of base styling for popovers which can cover most all usage.

At worst, the styling could be moved to the component which renders the LinkControl within a Popover. As noted at #18061 (comment), there is an option to explore to repurpose the (largely defunct) URLPopover to this end.

[richtabor]

@getdave Is this still relevant? Thanks.

[getdave]

I think it can be closed.