window: Avoid double event processing in the multipress event controller

The events to those are fed outside the regular event propagation scheme,
through _gtk_window_check_handle_wm_event(), so set the controller to
GTK_PHASE_NONE so events aren't processed first manually, and then
automatically.
widget: Change GtkCapturePhase behavior in event controllers' handling

Previously, there would be globally just a capture and a bubble phase,
with the event just going down the hierarchy once, and the up once.
GTK_PHASE_TARGET actually meaning "run within event handlers", so in
a hierarchy of 3 widgets, emission would be:

  Capture(C)
  Capture(B)
  Capture(A)
  Target(A) (if event handlers allow)
  Bubble(A)
  Target(B) (if event handlers allow)
  Bubble(B)
  Target(C) (if event handlers allow)
  Bubble(C)

This commit changes this behavior and uses GTK_PHASE_TARGET in a less
misleading way, running only on the widget that was meant to receive
the event. And GTK_PHASE_BUBBLE has taken over the execution place of
GTK_PHASE_TARGET, so the emission remains:

  Capture(C)
  Capture(B)
  Capture(A)
  Target(A)
  Bubble(A) (if event handlers allow)
  Bubble(B) (...)
  Bubble(C) (...)

As it was, GTK_PHASE_BUBBLE was useful for running event controllers
paralelly to event handlers, without modifying a single line in those.
For those mixed scenarios, Any of the other phases will have to be
used at discretion, or the event handlers eventually changed to chain
up and let the default event handlers in GtkWidget to be run.
gtk: Update GtkGesture users to the GtkPropagationPhase semantics change

Mainly doing s/TARGET/BUBBLE/ on the fully ported widgets, but GtkTreeView
where the double click handler has moved to GTK_PHASE_TARGET so it runs
parallelly to the still existing event handlers.
eventcontroller: Hide more details

Signals are left hidden, so the only entry point to handle_event/reset
is API.
gesture: Fix wrong assert in gtk_gesture_set_window

The window must be part of the event controller widget, so
fix the inverted logic.
button: Claim the sequence on multipress::pressed

In order to avoid the event from bubbling, as it used to (not) do.
treeview: Make the multipress gesture listen only to bin_window

This gesture is meant to handle row-activated signaling, so make the
gesture ignore events from any other window.