Set uBit.io.logo to capacitive touch mode by default.

[microbit-carlos]

@finneyj this would be the simplest way set the io.logo pin capacitive, do you think it should be behind a build flag as well? If so, what would be the best name for it? MICROBIT_PIN_LOGO_CAPACITIVE?
In that case we would still like to make sure the default value is set to capacitive, so the flag would be mostly used to disable this feature?

[github-actions]

Build diff

Base commit: 9a03c691c12474852819843f21e32908ab405a2f
Action run: https://github.com/lancaster-university/codal-microbit-v2/actions/runs/8453920050

     VM SIZE    
 -------------- 
  +0.8%     +20    /home/runner/work/codal-microbit-v2/codal-microbit-v2/libraries/codal-microbit-v2/model/MicroBit.cpp
  -0.0%      -4    [section .text]
  +0.0%     +16    TOTAL

[microbit-carlos]

We can change the state of the io pin to configure the capacitive state without running the ADC and any background events that might be triggered.

[github-actions]

Build diff

Base commit: a3492c4378be02a0071721dbc5a7164840be5a11
Action run: https://github.com/lancaster-university/codal-microbit-v2/actions/runs/9176454307

     VM SIZE    
 -------------- 
  +0.5%     +12    /home/runner/work/codal-microbit-v2/codal-microbit-v2/libraries/codal-microbit-v2/model/MicroBit.cpp
  -0.1%     -12    [section .text]
  [ = ]       0    TOTAL

[microbit-carlos]

Reviewed on a call with @finneyj and ready to be merged.