Using a tooltip to inform when the calendar is read-only won't
work in touch devices.
This change also improves a11y, as Orca now reads this message,
something that wasn't happening before.
Non-technical users may not realize why they can not edit some events
from read-only subscribed remote calendars.
A symbolic padlock icon does not suffice to make this obvious.
This tooltip makes the UI self-documenting, and improves accessibility.
Use a GtkListBox and bind from the model. Create rows from the model
items, and bind properties as needed.
The action target is set only when the calendar is writable because
setting an invalid action+target pair makes the row insensitive.
Remove the ancient menu icon hack.
GtkDialog is being deprecated. Instead of using it,
we want to subclass AdwWindow. As part of this change
the content and headerbar are put together in one box.
These are still hardcoded instead of measuring the available space,
but it's better than nothing in the meantime.
Decent WMs size the window correctly if width/height exceed the screen.
Also, allow the Notes field to expand vertically, to fill the space.
Fixes https://gitlab.gnome.org/GNOME/gnome-calendar/-/issues/602
Using dialog responses to communicate intent to GcalWindow was always
a hack, and as the code is cleaned, it's getting increasingly annoying.
Replace this with a proper 'remove-event' signal ('delete-event' would
conflict with the equally named GTK signal), remove the custom response
types, and cleanup the code.
