tests: move test lnd logs to a more permanent location

[orbitalturtle]

Here's a first stab at drafting a solution for storing logs, as discussed with @carlaKC in #58 . The code changes are pretty small, but a couple notes below on implementation, including a change to LDK that we need to do to get this fully working.

A couple of notes on implementation:

• I went with storing the LND logs in a custom /tmp directory for each test. The motivation being that this keeps the logs around after the test so developers can use it for debugging, but since the logs likely won't be needed for long, it's nice to have them stored in the /tmp file so that they're automatically deleted by the OS after a certain amount of time/when the device restarts.
• It's possible to specify a custom path for LND logs. But this is not supported by LDK quite yet. Should be easy to add support, I'm pinging Elias from LDK about doing a quick PR for this, if that sounds good. Then we can finish up the LDK side of things.

[carlaKC]

Seems reasonable! We're also going to want these logs uploaded as an artifacts in GH actions so that we can see what's failing (generally slower CI machines tend to flake a lot more so local copies often aren't enough). Can we look into that here as well?

[orbitalturtle]

@carlaKC ok I added the github action for uploading the logs :) I also now included the ldk logs since this PR for setting the ldk logs elsewhere is now merged lightningdevkit/ldk-node#129

[dunxen]

This looks good.

The comment is optional if you'd like some other ldk-node fixes in but don't they actually affect us.

[dunxen]

Let's quickly get in some of the other bug fixes :)

Suggested change

	ldk-node = { git = "https://github.com/lightningdevkit/ldk-node", rev = "3a31209" }
	ldk-node = { git = "https://github.com/lightningdevkit/ldk-node", rev = "77acd3b" }

[carlaKC]

Replaced by #70