Use type safety to prevent provider addr vs consumer addr bugs

[shaspitz]

Problem

Issues like #693 have proven that using provider and consumer addresses interchangeably as the same type can cause bugs. We should make a new protobuf key type wrapper that can delineate between a provider cons address and a consumer cons address.

Closing criteria

Protobuf type(s) are made and implemented across our repo to prevent developers from mistakenly using the wrong type of address. This issue could also be closed by simply using golang type aliases

[shaspitz]

As an example Methods like SetSlashAcks should accept consumerConsAddr instead of a string, this would have prevented #693. See also #694 (comment)