For now, this implements the functionality required for esp32 and rp2,
including support for numeric pins, rp2 alternate functions, and rp2
extended pins.
This also updates the rp2 port to use the same structure for pins.h and
pins.csv as for esp32, and moves the pin definitions directly into the
table (rather than having a table of pointers), which is a small code size
improvement.
Support for "hidden" pins in pins.csv is added (matching the stm32
implementation).
This work was funded through GitHub Sponsors.
Signed-off-by: Jim Mussared <jim.mussared@gmail.com>
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