The customize routes add CSS classes that make these admin
config pages look different from the ones under /admin/config.
We want all config routes to be under /admin/config as well.
This commit moves the emoji, user fields, and permalinks pages
out of customize and into config, updating all references and
adding more rails routes as needed.
Also renames admin emojis route to emoji, emoji is singular and plural.
This converts the `<AdminPageHeader />` component and the
`<AdminPageSubheader />` components into new components
that can be used outside of admin, and updates the CSS classes.
Also introduces a `<DPageActionButton />` component and child
components for the header action buttons.
I have to keep the old admin-only components around for
now until plugins are updated, then we can remove it,
and remove the re-exports that are done within
admin-page-action-button.gjs
1. Use `this.` instead of `{{action}}` where applicable
2. Use `{{fn}}` instead of `@actionParam` where applicable
3. Use non-`@` versions of class/type/tabindex/aria-controls/aria-expanded
4. Remove `btn` class (it's added automatically to all DButtons)
5. Remove `type="button"` (it's the default)
6. Use `concat-class` helper
