[avalanche] Account for our own proof in the connected stake computation

Summary:
If we are not connected to another node using our proof, account for a connection anyway as long as our proof is bound to a peer.

Depends on D11366.

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, tyler-smith

Reviewed By: #bitcoin_abc, tyler-smith

Subscribers: tyler-smith

Differential Revision: https://reviews.bitcoinabc.org/D11367