Multi-region SKU support for Steelseries Apex Pro

Patchset which adds the following to the Steelseries Apex Pro, Apex 7, their TKL versions and possibly the Apex 5.

• Implements serial/model number and firmware version retrieval of connected boards.
• Removes the dedicated Apex TKL controller instance, unify with the regular Apex.
• Proposed method of allowing the LED map of regional SKUs to be set as part of device detection. At the moment US, UK, JP and Nordic keyboards are implemented.

This has been tested on a Japanese Apex Pro, Nordic Apex 7 and US Apex 7 TKL.

The matrix patching method probably is not expected after it was suggested that the way AsusAuraUSBController does things is a possible way forward. I couldn't think of a straight forward way to account for per-region key overloads (` and E/J, the swapping of [,] and @) without resorting to mass duplication with the current way the SteelSeriesApex implementation is wired up. Happy to look at other options if this isn't appropriate.