Input: Process input events in batches (#7483)

Requires https://github.com/koreader/koreader-base/pull/1344 & https://github.com/koreader/koreader-base/pull/1346 (fix #7485)

Assorted input fixes:

* Actually handle errors in the "there's a callback timer" input polling loop.
* Don't break timerfd when the clock probe was inconclusive.

Not directly related, but noticed because of duplicate onInputEvent handlers:

* HookContainer: Fix deregistration to actually deregister properly. "Regression" extant since its inception in #2933 (!).
* Made sure the three plugins (basically the trio of AutoThingies ;p) that were using HookContainer actually unschedule their task on teardown.

frontend/ui/uimanager.lua

@@ -1549,7 +1549,7 @@ end
 -- Process all pending events on all registered ZMQs.
 function UIManager:processZMQs()
     for _, zeromq in ipairs(self._zeromqs) do
-        for input_event in zeromq.waitEvent,zeromq do
+        for input_event in zeromq.waitEvent, zeromq do
             self:handleInputEvent(input_event)
         end
     end
@@ -1611,12 +1611,15 @@ function UIManager:handleInput()
     -- Anywhere else breaks preventStandby/allowStandby invariants used by background jobs while UI is left running.
     self:_standbyTransition()
 
-    -- wait for next event
-    local input_event = Input:waitEvent(now, deadline)
+    -- wait for next batch of events
+    local input_events = Input:waitEvent(now, deadline)
 
-    -- delegate input_event to handler
-    if input_event then
-        self:handleInputEvent(input_event)
+    -- delegate each input event to handler
+    if input_events then
+        -- Handle the full batch of events
+        for __, ev in ipairs(input_events) do
+            self:handleInputEvent(ev)
+        end
     end
 
     if self.looper then
@@ -1637,7 +1640,7 @@ end
 
 
 function UIManager:onRotation()
-    self:setDirty('all', 'full')
+    self:setDirty("all", "full")
     self:forceRePaint()
 end