fix: allow onion addresses and external peers in messages command

[nkatha23]

• Add is_external_peer() helper to detect onion addresses and non-tank peers
• Skip namespace parsing and kubectl IP lookups for external peers
• Match message capture directories directly by address for external peers
• Fix dot-split validation that would reject onion addresses containing dots
• Add check_messages() test to onion_test.py to verify the fix

Fixes #761

[nkatha23]

@pinheadmz I investigated the rpc_test failure and I believe it's a pre-existing issue unrelated to my changes.
The test/data/12_node_ring/node-defaults.yaml does not include -capturemessages, which means Bitcoin message capture is never enabled for that test network. Without it, get_messages will always return an empty list and the verack assertion will always fail.
My changes only affect how tank_b is resolved — for known tanks the kubectl IP lookup path is unchanged. The rpc_test failure would occur on main as well.
Happy to also fix the node-defaults.yaml to add -capturemessages if that's the right approach, or open a separate issue for it. Let me know how you'd like to proceed.

[nkatha23]

14/16 checks passing. The only remaining failure is plugin_test which is a pre-existing issue in test_base.py, while investigating it I discovered that inspect.getsource() can't handle functools.partial objects, causing a TypeError that masks the real timeout error. I've opened a separate PR #795 to fix that. This PR is ready for review.

[pinheadmz]

rebased on main after merging #803

[pinheadmz]

code review 4189232

Thanks for taking this on! I left a few comments below but in general, please squash any fixes you make within the branch. To me it looks like this whole PR could be one single commit.

And then, I think the approach could be improved. I think messages() could be entirely left alone, and only in get_messages() we fall back to whatever the exact value of tank_b: str is if we fail to map that tank name to an IP address with a directory in message_capture.

I don't think namespace_b is None should be a trigger for the alternate behavior.

Also I wonder if we can add the port internally? Instead of the user needing to suffix ._18444 or whatever?

[nkatha23]

Hello @pinheadmz, I've addressed all review feedback:

Removed is_external_peer() helper
Restored messages() to original shape, fixed typo
Updated get_messages() with try/except kubectl fallback, if IP lookup fails, falls back to matching tank_b directly against directory names
Inlined onion message check into check_tor per your diff
Squashed all commits into one