Move most logs in the chain module to the debug level

[tankyleo]

When the node is idle, the info level was quite spammy. It is now quiet.

[ldk-reviews-bot]

👋 Thanks for assigning @benthecarman as a reviewer!
I'll wait for their review and will help manage the review process.
Once they submit their review, I'll check if a second reviewer would be helpful.

[benthecarman]

lgtm, however might be useful to just have a single info log that says each time a sync happens.

[tankyleo]

lgtm, however might be useful to just have a single info log that says each time a sync happens.

My intention is to avoid periodic information logs at the info level. I want to let the node sit for a week, and if nothing happened, no issues, nothing out of the ordinary, then no logs :)

Maybe I could just watch Warn and Error, but if I am generating an address for example, or connecting to a peer / opening a channel, that should be an info, not a warn. And I won't want these events to be hidden among the many "sync happened" logs over a week.