Feeders push checkpoints even if they are equivalent

[mhutchinson]

The feeder previously short circuited if the witness had already witnessed an equivalent checkpoint. This meant that logs would get stale timestamps from the witnesses. This change makes it so that the witness will keep updating their timestamps on checkpoints.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 5 lines in your changes missing coverage. Please review.

Project coverage is 31.30%. Comparing base (3c58af4) to head (c57c23a).
Report is 119 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/feeder/feeder.go	0.00%	4 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #283       +/-   ##
===========================================
- Coverage   51.05%   31.30%   -19.75%     
===========================================
  Files          11       23       +12     
  Lines         903     1757      +854     
===========================================
+ Hits          461      550       +89     
- Misses        374     1109      +735     
- Partials       68       98       +30     

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