Reader: Do less work on same-orientation non-gyro rotations (#11297)

Namely, don't recompute layouts, as they do not change.
(The gyro codepaths were already doing something similar.)

* Keep ConfigDialog, FileManagerMenu & ReaderMenu open on rotation.
  (In practice, only ConfigDialog is affected, as *Menu doesn't handle the rotation event.)
* Plugged an instance leak in the aforementioned Menu classes.
* Unify behavior & code with the gyro codepaths.

frontend/apps/reader/modules/readermenu.lua

@@ -95,7 +95,7 @@ function ReaderMenu:getPreviousFile()
     return require("readhistory"):getPreviousFile(self.ui.document.file)
 end
 
-function ReaderMenu:onReaderReady()
+function ReaderMenu:initGesListener()
     if not Device:isTouchDevice() then return end
 
     local DTAP_ZONE_MENU = G_defaults:readSetting("DTAP_ZONE_MENU")
@@ -179,6 +179,8 @@ function ReaderMenu:onReaderReady()
     })
 end
 
+ReaderMenu.onReaderReady = ReaderMenu.initGesListener
+
 function ReaderMenu:setUpdateItemTable()
     for _, widget in pairs(self.registered_widgets) do
         local ok, err = pcall(widget.addToMainMenu, widget, self.menu_items)
@@ -456,16 +458,24 @@ function ReaderMenu:onShowMenu(tab_index)
 end
 
 function ReaderMenu:onCloseReaderMenu()
-    if self.menu_container then
-        self.last_tab_index = self.menu_container[1].last_index
-        self:onSaveSettings()
-        UIManager:close(self.menu_container)
-    end
+    if not self.menu_container then return true end
+    self.last_tab_index = self.menu_container[1].last_index
+    self:onSaveSettings()
+    UIManager:close(self.menu_container)
+    self.menu_container = nil
     return true
 end
 
 function ReaderMenu:onSetDimensions(dimen)
-    self:onCloseReaderMenu()
+    -- This widget doesn't support in-place layout updates, so, close & reopen
+    if self.menu_container then
+        self:onCloseReaderMenu()
+        self:onShowMenu()
+    end
+
+    -- update gesture zones according to new screen dimen
+    -- (On CRe, this will get called a second time by ReaderReady once the document is reloaded).
+    self:initGesListener()
 end
 
 function ReaderMenu:onCloseDocument()