refactor: downgrade stale _last_checkpoint log from warn! to info!

[sebastiantia]

What changes are proposed in this pull request?

Downgrade warn! to info! when _last_checkpoint is stale. Since _last_checkpoint is only a hint and may frequently be out of date in a busy system, logging it as a warning is unnecessary. Clients can still see the info-level log if needed.

[nicklan]

thanks!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.62%. Comparing base (9290930) to head (ade2a23).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #777      +/-   ##
==========================================
- Coverage   84.64%   84.62%   -0.03%     
==========================================
  Files          82       82              
  Lines       19735    19735              
  Branches    19735    19735              
==========================================
- Hits        16705    16701       -4     
- Misses       2214     2216       +2     
- Partials      816      818       +2     

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[zachschuermann]

from @scovich: let's do info! by default but warn! if outside log retention duration

[sebastiantia]

@zachschuermann Took a quick look, it will be a bit challenging to leverage the history retention window since the checkpoint hint does not include the creation timestamp, only version.

To leverage the retention window, we would need to pull the last checkpoint's file metadata during log listing which requires more changes than a warning might be worth? Thinking about merging this one for now and tracking the other with an issue. #791