feat(log): Add a config for writing logs to a file

[teor2345]

Motivation

Zebra can't currently write logs to a file - it requires extra shell redirections or a service harness.

This might be confusing for some users.

Solution

• Add a config with a file path for logging
• If configured, append logs to that file

Review

This is a low-priority extra Zebra feature.

Reviewer Checklist

• Will the PR name make sense to users?
  • Does it need extra CHANGELOG info? (new features, breaking changes, large changes)
• Are the PR labels correct?
• Does the code do what the ticket and PR says?
  • Does it change concurrent code, unsafe code, or consensus rules?
• How do you know it works? Does it have tests?

[codecov]

Codecov Report

Merging #6449 (e3088ef) into main (5db2243) will decrease coverage by 0.07%.
The diff coverage is 62.50%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6449      +/-   ##
==========================================
- Coverage   77.78%   77.72%   -0.07%     
==========================================
  Files         304      304              
  Lines       39637    39640       +3     
==========================================
- Hits        30833    30811      -22     
- Misses       8804     8829      +25     

[arya2]

This is great!