Rename PNode #58
Description
Rename node library
Obviously, node is the perfect name for this library, but it leads to confusion for dune when using it on Deku (I guess, the struggle will be the same for a lot of blockchain client...)
[Quick description of the change you want to make or add]
Client and Node cannot be merged because of dependency cycle with Failure_detector.
Going for a synonym of Node like knot looks not pretty good, and using a flower term, doesn't seem explicit enough (pistil for example)