Meta: discuss named return values in interfaces

[awfm9]

My opinion on this is that we should name parameters and return values according to the same principle, which is:

• if the parameter types could be ambiguous, make the parameter names explicit;
• otherwise, if the parameter types are already clear, omit the parameter names.

// DON'T
type Something interface {
   LoadBlock(blockID flow.Identifier) (block *flow.Block, err error)
}

// DO
type Something interface {
  LoadBlock(flow.Identifier) (*flow.Block, error)
}

// DON'T
type Something interface {
  LoadBlock(uint64) (flow.Identifier, flow.Identifier, error)
}

// DO
type Something interface {
  LoadBlock(height uint64) (blockID flow.Identifier, parentID flow.Identifier, err error)
}

Within an interface, we can use both approaches, depending on what makes sense.