Remove feeders from omniwitness

[AlCutter]

This PR removes the feeders from omniwitness.

Feeders were originally added as a means to "opt-in" logs to witnessing without requiring their participation. This was helpful during the early days of experimentation, but is less important now that we have tlog-witness, the public witness network, and log implementations like Tessera which natively integrate the equivalent of feeding.

The feedwitness binary remains, for the time being, which allows folks who still want the ability to feed logs to continue doing so.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 9.21053% with 69 lines in your changes missing coverage. Please review.
✅ Project coverage is 24.20%. Comparing base (362a011) to head (052e1ec).

Files with missing lines	Patch %	Lines
cmd/feedwitness/configs.go	0.00%	32 Missing ⚠️
cmd/feedwitness/run_feeders.go	17.94%	32 Missing ⚠️
cmd/feedwitness/main.go	0.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #548      +/-   ##
==========================================
- Coverage   24.91%   24.20%   -0.71%     
==========================================
  Files          30       31       +1     
  Lines        2107     2115       +8     
==========================================
- Hits          525      512      -13     
- Misses       1488     1515      +27     
+ Partials       94       88       -6     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.