Create a new utils function gimp_tools_show_tool_options() because
showing the tool options is likely a common action. And use this when we
want to blink the selection mode box, for this particular case.
Note that I could not reproduce the CRITICAL here (i.e. even if the
dockable was not showing, it seems the widget did already exist anyway).
Anyway it's a nice idea to raise the tool options as the goal is to
explicitly show how to fix the issue here. And it should fix the bug for
people encountering it.
This function will help us raise attention to various widgets in
dockables by blinking them similarly to how we blink locks or visibility
icons.
I associate this with the fact that property widgets identifier will be
the property name, so we get identifiers for free when creating widgets
through the propwidgets API.
Add gimp_tools_blink_lock_box() utility function, in a new
gimptools-utils.c file, which takes a GimpItem, and blinks the
GimpItemTreeView lock-box of the corresponding dockable. This can
be used to hint that the item's lock toggles are preventing it from
being edited.
