pytest: Test the mindepth customizations of fundchannel and hook

Just test that we can customize, and we'll add mindepth=0 support in
the next couple of commits.

tests/plugins/zeroconf-selective.py

@@ -0,0 +1,34 @@
+#!/usr/bin/env python3
+"""Use the openchannel hook to selectively opt-into zeroconf
+"""
+
+from pyln.client import Plugin
+
+plugin = Plugin()
+
+
+@plugin.hook('openchannel')
+def on_openchannel(openchannel, plugin, **kwargs):
+    plugin.log(repr(openchannel))
+    mindepth = int(plugin.options['zeroconf-mindepth']['value'])
+
+    if openchannel['id'] == plugin.options['zeroconf-allow']['value']:
+        plugin.log(f"This peer is in the zeroconf allowlist, setting mindepth={mindepth}")
+        return {'result': 'continue', 'mindepth': mindepth}
+    else:
+        return {'result': 'continue'}
+
+
+plugin.add_option(
+    'zeroconf-allow',
+    'A node_id to allow zeroconf channels from',
+    '03864ef025fde8fb587d989186ce6a4a186895ee44a926bfc370e2c366597a3f8f'
+)
+
+plugin.add_option(
+    'zeroconf-mindepth',
+    0,
+    'Number of confirmations to require from allowlisted peers',
+)
+
+plugin.run()