[avalanche] Add field to the getavalancheinfo RPC to monitor if our proof is shared

Summary:
Since D13030 the node is waiting for an inbound connection before it can share the local proof with the avalanche network. This diff adds a new field to the getavalancheinfo RPC to monitor this status.

Depends on D13030.

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, sdulfari

Reviewed By: #bitcoin_abc, sdulfari

Subscribers: sdulfari

Differential Revision: https://reviews.bitcoinabc.org/D13050