Add log for when retention job starts

[wslulciuc]

Problem

Let's add a log event when the DbRetentionJob starts. The log will display:

• Retention policy
• Run frequency

Solution

INFO  [2023-07-25 13:47:10,615] marquez.jobs.DbRetentionJob: Started db retention job with retention policy of '7' days, scheduled to be applied every '1' mins.

Checklist

• You've signed-off your work
• Your changes are accompanied by tests (if relevant)
• Your change contains a small diff and is self-contained
• You've updated any relevant documentation (if relevant)
• You've included a one-line summary of your change for the CHANGELOG.md (Depending on the change, this may not be necessary).
• You've versioned your .sql database schema migration according to Flyway's naming convention (if relevant)
• You've included a header in any source code files (if relevant)

[codecov]

Codecov Report

Merging #2551 (2c6861c) into main (3aa0b5b) will decrease coverage by 0.05%.
The diff coverage is 0.00%.

@@             Coverage Diff              @@
##               main    #2551      +/-   ##
============================================
- Coverage     83.30%   83.26%   -0.05%     
  Complexity     1286     1286              
============================================
  Files           243      243              
  Lines          5931     5934       +3     
  Branches        279      279              
============================================
  Hits           4941     4941              
- Misses          843      846       +3     
  Partials        147      147              

Files Changed	Coverage Δ
api/src/main/java/marquez/jobs/DbRetentionJob.java	0.00% <0.00%> (ø)

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[phixMe]

Looks good.