doc: Update NetBSD Build Guide #31586

This PR:

1. Updates the documented NetBSD version.

2. Adds the optional ZeroMQ package to align the guide with other *BSD systems.

3. Updates the Python version to meet the minimum requirement specified in #30527.

4. Suggests to Install net/py-zmq package to enable the interface_zmq.py functional test.

5. Fix a formatting issue.

See also the recent NetBSD nightly build at https://github.com/hebasto/bitcoin-core-nightly/actions/runs/12554769828/job/35003929261.

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Code Coverage & Benchmarks

For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/31586.

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ACK 2bdaf52ed1259fd3bec22b680e12563fcee0a8b3

Dry ran the guide with a fresh NetBSD (10.1) installation, built with zmq, and tested zmqpubhashblock=tcp://127.0.0.1:28334 with an adhoc python zmq client (as expected, saw the topic, block hash, and sequence arrive when generating blocks in regtest with -generate).

import zmq
context = zmq.Context()
socket = context.socket(zmq.SUB)
socket.connect("tcp://127.0.0.1:28334")
filter = "hashblock"
socket.setsockopt_string(zmq.SUBSCRIBE, filter)
while True:
    print(socket.recv().hex())

Also successfully ran the functional test suite (python). Had to create a symlink (python3 --> python3.10).

@tdb3

Thank you for reviewing!

Also successfully ran the functional test suite (python). Had to create a symlink (python3 --> python3.10).

A symlink won't be necessary after #31541.