Workaround for crashing when many tooltips are shown consecutively

[flodavid]

Add delay of 100ms before showing dock tooltips:
Fixes #559. After researching it, the culprit seems to be the Nvidia driver, which causes a problem with GTK.Popup, which is used as tooltips when hovering launchers in the doc since #441.

Adding a big enough delay before showing the tooltip seems to prevent the error (or at least making it very unlikely). I tried 1ms and it seemed to reduces the crashes quite a bit already, but I succeeded with 50ms by increasing the pointer speed, so I set it to 100ms.
This can also have a positive side effect: When rapidly hovering the launchers, every tooltip were briefly shown, but not long enough to be readable. So the delay makes it less distracting a restores the behaviour before #441.

I only added the delay to the Launcher class, and not the parent BaseItem. Feel free to rework the PR or close it to implement a cleaner fix. Maybe a proper fix should be added to GTK, but a simple workaround by adding a delay like here would not be acceptable I guess.

[flodavid]

I moved the code to BaseItem since existing code was moved out of Launcher (I tested with the latest changes and crash still happens without this PR), and rebased to fix conflicts

[ryonakano]

Probably you can use GLib.Source.remove () instead of a normal flag?

[flodavid]

You are probably right. I will do that soon

[flodavid]

Is this what you had in mind ? b6968f1
Edit: I removed open_tooltip_timeout_id = 0; in leave () since I assume leave () cannot be called twice without enter () being called in between and the ID being modified by it. Is it safe to assume or am I risking race condition ? Even then, the event ID would need to be reassigned to another event for it to cause a problem. Is this enough to justify not needing the reset ?

[flodavid]

I think the pipeline is not failing because of the modification in this PR, as it also fails in another PR.
The error seems to be:

../src/WindowSystem/WindowSystem.vala: In function 'dock_window_system_find_window':
../src/WindowSystem/WindowSystem.vala:46:53: error: passing argument 2 of 'g_ptr_array_find_with_equal_func' makes pointer from integer without a cast [-Wint-conversion]
   46 |         if (windows.find_custom (uid, (win, uid) => {
      |                                                     ^  
      |                                                     |
      |                                                     guint64 {aka long unsigned int}
In file included from /usr/include/glib-2.0/glib.h:33,
                 from /usr/include/glib-2.0/gobject/gbinding.h:30,
                 from /usr/include/glib-2.0/glib-object.h:24,
                 from src/io.elementary.dock.p/WindowSystem/WindowSystem.c:9:
/usr/include/glib-2.0/glib/garray.h:262:61: note: expected 'gconstpointer' {aka 'const void *'} but argument is of type 'guint64' {aka 'long unsigned int'}
  262 |                                              gconstpointer  needle,
      |                                              ~~~~~~~~~~~~~~~^~~~~~

and it is unrelated to my edits.