ctxlink/wifi: fix the speed issues with the Wi-Fi interface

[sidprice]

The reading of the ADC to acquire the target and battery
voltages was being done in a blocking manner and at
a place in the code that blocked the timely servicing
of the Wi-Fi channel.

In this updated code the ADC is read in the Timer service of the Wi-Fi Server.
There are two channels and each channel conversion is started on one timer service and read on the next timer service. Giving four phases of operation.

Also, the ADC reading code is only run every 100ms.

Your checklist for this pull request

• I've read the Code of Conduct
• I've read the guidelines for contributing to this repository
• It builds for hardware native (see Building the firmware)
• It builds as BMDA (see Building the BMDA)
• I've tested it to the best of my ability
• My commit messages provide a useful short description of what the commits do

Closing issues

None.

[dragonmux]

This definitely gets most of the way there and we like what we see! There are only two major comments here which are about using the GCC-specific compiler intrinsics rather than the stdlib functions, and as a result a couple of parameters winding up backwards which might compile with the builtins, but which shouldn't as it does alter the meaning of the code. Using the stdlib functions prevents this due to how they're typed.

[dragonmux]

This all LGTM, merging. Thank you for the contribution and congrats on the speed doubling (if not slightly more) of the WiFi interface on your ctxLink!