Add reloadIntervalActive and reloadIntervalInactive settings.

1. default reload interval -> used by default (15 seconds)
2. reload interval active -> used when an "active" process like scan is
  running (3 seconds)
3. reload interval inactive -> used when a page will "inactive" (60
  seconds)

Add handlers for visibility changed events. If the current window/tab
gets hidden the next reload interval will be "inactive" (60 seconds). If
the window/tab gets activated again to current timer will be aborted and
a new timer will be started. This new timer can be an active (3 seconds)
or default (15 seconds) reload timer depending on the current page
state.

Some of the behavior is tested only indirectly (e.g the exact used
interval) because with class components it isn't possible to access and
test internals.

removeVisibilityListender -> removeVisibilityListener

Co-Authored-By: Steffen Waterkamp <[email protected]>