Patched `ps` that reports used memory for Pi Pico

[veremenko-y]

For pico every program is located at PROGBASE, so substracting it from p_top and rounding up to the ram block size (4k) will result in the correct value of memory allocated for process.

[EtchedPixels]

Still thinking about this. It's nice to have the value but patching ps magically is the wrong way to do it, and ps having secret knowledge is not much better.

[veremenko-y]

No worries. I understand why you're not sure. I think the only proper way to keep track of it is to add it to p_tab which brings a lot consequences with it...

[EtchedPixels]

Core stuff done. Just needs the target to set p->size