When creating a new event or converting an all-day event to time-based, pre-set start time to current time (and set the end time +1H), instead of midnight

When creating a new event, the current hour is set to 00:00 for both start and end, which tends to cause all sorts of issues. It could improve the UX (and avoid some issues) if the selected hour would be pre-set to the current time for start and end +1H.

Edit / implementation tips by @jfft:

• If the current time is in the middle of the night (i.e.; after midnight and before 6 AM), assume the user is going to need to sleep and doesn't want to schedule something in the middle of the night, and consider that the next probable default start time is at least 8 hours from now.
• Watch out if the current time is 23:xx, to avoid causing issue #1121.
• Also watch out for AM/PM issues like #1120.
• When converting the metadata to toggle off all-day mode, if there was already some start/end time metadata that weren't midnight, evaluate those as possible defaults instead of guessing (see #889 (comment 1672248))