Add a [ERR] filter for LND logs

[Darth-Coin]

Describe your enhancement idea

When the user is trying to debug a Zeus issue, usually will go to LND logs to see what is going on.

• some users will get lost in the long list of [INF] events and could miss the [ERR] ones or not even understanding all.
• when the user wants to copy the logs to share them with devs, usually is copying only a truncated part of them, not from the beginning. If we can filter only the ones [ERR] will be a shorter content and only the ones that could be related to the issue.

[kaloudis]

Proof of concept started in https://github.com/ZeusLN/zeus/pull/2165

[Darth-Coin]

I was testing this proof of concept version and I would like to make some mentions to be noted:

• when you set the DEBUG level and restart, is using a lot of memory and app could freeze
• only the INFO level was more or less "manageable", all the rest were crashing the app
• with this version, using any log level, when you try to scan an invoice the app is crashing instantly

I suggest also to add the option to change the log level in the startup screen -> node setup. So user do not have to restart all the time in order to switch the log level. Or if is possible to not be necessary to restart the node, just to see a specific level of logs.

[kaloudis]

https://lightning.engineering/api-docs/api/lnd/lightning/debug-level

[tlindi]

Maybe filtering could be usable also in case of https://github.com/ZeusLN/zeus/issues/2055 Which requirement(s) is now filled in LND 0.18.0-beta.