ButtonTable: reset MovableContainer state on button tap

Prevent any later hold_release event from being handled
by MovableContainer as a moving touch+hold_release.
This issue was noticable when closing DictQuickLookup
with long-press on close, resulting in the movable
highlight actions ButtonTable moving to where the
long-press happened.

frontend/ui/widget/container/movablecontainer.lua

@@ -342,4 +342,11 @@ function MovableContainer:onMovablePanRelease(_, ges)
     return false
 end
 
+function MovableContainer:resetEventState()
+    -- Cancel some internal moving-or-about-to-move state.
+    -- Can be called explicitely to prevent bad widget interactions.
+    self._touch_pre_pan_was_inside = false
+    self._moving = false
+end
+
 return MovableContainer