Clean up chain exchange responses and peer disconnects

[austinabell]

Summary of changes
Changes introduced in this pull request:

• Changes chain exchange channel type to be result to pass in internal libp2p errors, was previously leaving to timeout
• Removes peers from cx peer list on error other than timeout
• Update shuffled peers prefix (amount of peers each request is sent to before failing)

With these changes, sync doesn't reset sporatically and duplicate faulty requests don't get sent

Reference issue to close (if applicable)

Closes

Other information and links