A first step in cleaning up RLP, which has lots of interesting issues -
the next step would be to clean up the exception handling as well
(Resultify?)
* remove `RlpNode` (unused)
* single-pass parsing for most functionality via RlpItem
* stricter conformance to spec
* remove float support
* warn about signed integers
* raise on invalid RLP earlier
* avoid several pointless allocations, in particular in `listLen`,
`listElem` etc
* include spec docs
* Add build_dcli target and add it to CI
* Fix local imports for dcli
* And use local imports for all other files too
* Use local imports in tests and rlpx protocols
Jacek Sieka
Ștefan Talpalaru
Kim De Mey
Yuriy Glukhov