Based on reports here https://meta.discourse.org/t/improved-bookmarks-with-reminders/144542
* Because the `userHasTimezone` property was computed and we were checking on an (essentially) global object, ember was not aware that the user timezone had changed because it changed in a different place. instead set the timezone as internal state for the modal on show and base the computed property off of that so it mutates correctly
* The tap-tile components were in the admin folder completely unnecessarily, move them out into the main discourse folder otherwise noone else can use the new bookmarks (icon + text is missing)
* Cosmetic fixes for the bookmark modal
* Do not show "later today" when the later time will be > 5pm
* When a custom reminder time is selected, store it in localStorage. The next time the modal is opened, if the last datetime is > now, then a new tile with "Last" will be shown that lets the user reselect that same time.
* Also add an explicit "No Reminder" option that is selected by default
Add enable_bookmark_at_desktop_reminders site setting default to false a new hidden site setting to hide the "At Desktop" reminder option so we can restrict this further until it is polished.
