Currently bootstrap nodes for discv5 and for the Portal nodes
were provided through separate cli arguments. This is however
confusing and cumbersome as typically when (currently) testing
a node will have both discv5 and the Portal networks enabled.
We merge them into one argument.
If a node happens not to support a Portal network, it will be
removed after message request failure.
Commit also contains additional clean-up and nim-eth bump.
* Rename FindNode to FindNodes as per spec
* Use consistently lower case starting camelCase for consts
Style guide nep1 allows for both CamelCase and camelCase for
consts, but we seem to use more often camelCase. Using this now
consistently.
* Change some procs to func
* Add SSZ Unions through case objects
* Add connection id content response test and improve other test vectors
* Implement content keys and ids for state network as per spec
Content keys case object is used so that it can be serialized and
deserialized as an SSZ Union.
* Let message Union in Portal wire protocol start at 0 as per new spec
* Allow for passing Portal specific bootstrap nodes
* Fix to also replaceNode when decodeMessage fails
* Add portal bootstrap node tests and reorder test cases
KonradStaniec
Kim De Mey