Pico should limit pins for GPIO based on runtime config and debug probe use

[andrewdavidmackenzie]

The Pi Pico embassy code and some associated functions use a number of the hardware pins for other uses.

Also when using the debug-probe, it uses a number of the pins:

• Uart
  • Physical Pin#1 (GPIO0)
  • Physical Pin Chose the UI framework #2 (GPIO1)

Pins that are ALWAYS used, should be filtered out of the PinDescription set returned to the UI

• put a labal describing why unavailable, and reduce options to zero

Add a feature ("debug-probe") that when used removes other GPIO pins used by the debug probe

• put a labal and describe why unavailable