[x11] Hold a passive grab on buttons only when needed

Due to a bug in the XI2 protocol, clients have to reset scroll valuators
on XI_Enter because the scroll valuators might have changed while the
pointer was elsewhere. The XI_Enter event is usually sent when an input
device enters the window, but it can also be generated by a passive grab.

If an XI_Enter event has been generated by a passive grab, the client
should not reset scroll valuators. Unfortunately, there is no any
reliable way for the client to determine if an XI_Enter event has been
sent in response to a deactivated passive grab. A correct fix for the
scroll issues in GTK apps would involve changes in the XI2 protocol.

As a work around, we can hold a passive grab only if the current mouse
wheel action is either "Activate and scroll" or "Activate, raise, and
scroll."

BUG: 394772
FIXED-IN: 5.19.3