improve DZX request workflow/reporting

[dalalama]

A contributor can request a DZX connection, but currently there's no notification to the accepting contributor to accept it.
currently doublezero link list --dzx lists all DZX connection and someone needs to grep to determine those that are outstanding to be requested - however this is difficult because you can't grep on the accepting contributor as only the requested contributor shows in the output.

1. It would be useful to have a notification to the accepting pubkey that an action is ready for them to take. I imagine this is a bit difficult to action.
2. Perhaps something like [to the effect of, but not exactly] doublezero link list --my-dzx-actions would show all the dzx links your pubkey need to accept and a complementary command would show all the dzx requests you have outstanding (unaccepted).

I'm sure there are many alternatives as well.