Rethink (dynamic?) physical pin management

[brainstorm]

We've experimented with dynamic pin allocation with limited success. The complexity tradeoff when mixing static allocation(s) of resources vs the ability to change, say, UART pins at runtime is... tricky.

For now we're opting for hardcoding suitable pins on the different espressif ICs (those that do not usually create conflict due to "strapping pins" situations and/or bootloader interference), but we'd be open to ideas on how to do better.

[brainstorm]

Note 47a9d7c, where we temporarily dropped part of this for a suitable future implementation.

[brainstorm]

@jubeormk1 mentioned:

Pins are defined both here and in main.rs::main() we will have to look into this