rlp2 is a package that aims to replace the existing erigon-lib/rlp
package and the erigon/common/rlp
it is called rlp2 for now because it requires breaking changes to
erigon-lib/rlp and i do not have the time right now to test all current
uses of such functions
however, the encoder/decoder characteristics of rlp2 might be desirable
for caplin, and also for execution layer parsing blob txns, so im
putting it in a folder called rlp2 (note that it exports package rlp for
easier switching later)
importantly, rlp2 is designed for single-pass decoding with the ability
to skip elements one does not care about. it also is zero alloc.
