[avalanche] Print the proofid in getavalancheoeerinfo

Summary: Most of the other RPC use or return a proofid, so printing it in getavalanchepeerinfo is more convenient during debugging.

Test Plan:

./test/functional/test_runner.py abc_rpc_getavalanchepeerinfo

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D11757