[Kobo] Support USBMS exports (#6552)

* \o/

* Make sure the (debug) event log doesn't end up in the fd table of our child processes...
Otherwise, it breaks USBMS.

* Close suspicious fds in the Wi-Fi scripts
To prevent any and all issues w/ USBMS down the road...

* Minor USBMS UI tweaks

* Always ask for confirmation to start on USBMS session on plug

* Bump base

https://github.com/koreader/koreader-base/pull/1161
https://github.com/koreader/koreader-base/pull/1162
https://github.com/koreader/koreader-base/pull/1163
https://github.com/koreader/koreader-base/pull/1165
https://github.com/koreader/koreader-base/pull/1167

frontend/ui/uimanager.lua

@@ -155,8 +155,13 @@ function UIManager:init()
         end
         self.event_handlers["Charging"] = function()
             self:_beforeCharging()
+            -- NOTE: Plug/unplug events will wake the device up, which is why we put it back to sleep.
             if Device.screen_saver_mode then
                 self:suspend()
+            else
+                -- Potentially start an USBMS session
+                local MassStorage = require("ui/elements/mass_storage")
+                MassStorage:start(true)
             end
         end
         self.event_handlers["NotCharging"] = function()