[GTK4] GtkEventControllerMotion Enter/Leave events are not handled

[joel-majano]

Describe the bug

As part of the migration to GTK4, Enter/Leave procs were created, but they haven't been hooked up to do what they're supposed to to replicate GTK3 behavior. This causes things like shell tooltips to not work as these were previously handled by enter_notify_event handlers.

To Reproduce

Snippet 1, with the line shell.setToolTipText("any text"); added

Expected behavior

Shell tooltip is shown when mouse hovered on top of shell.

Environment:

1. Select the platform(s) on which the behavior is seen:

• Linux

2. Additional OS info (e.g. OS version, Linux Desktop, etc)

• Fedora 36, GTK 4.6.5

4. JRE/JDK version

• OpenJDK 17

Tracked in #228

[joel-majano]

This continues work from https://git.eclipse.org/r/c/platform/eclipse.platform.swt/+/183457 and https://bugs.eclipse.org/bugs/show_bug.cgi?id=539524.