- Allow access to contentDB from portal wire protocol
- Use this to do the db.get in `handleFindContent` directly
- Use this to check the `contentKeys` list in `handleOffer`
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.
