Add support to communicate with more than 2 IO Controllers (improve SharedDevice)

The current Profinet IO Device protocol stack (and firmware) v3.8.x supports Shared Device with 2 connections (2 IO ARs). This shall be extended to up to 8 ARs.
The existing Taglist entry to configure the amount of ARs shall allow to select the number of additional ARs in the range from 0 (no SharedDevice) to 7 (represents 8 IO ARs).

Technical restrictions (e.g. reachable cycle time and IO size depending on amount of ARs) need to be evaluated and documented. This can not be done upfront as it is a performance issue.