Handle NoEntries cid gracefully and improve cli output

[masih]

When encountering NoEntries CID, do not attempt to traverse it in
provider CLI.

Do not traverse entries of a removal advertisement even if a CID is
present. Instead, print useufl messages to signal such cases.

Improve output for human readability.

Fixes #179

[codecov-commenter]

Codecov Report

Merging #181 (6bef041) into main (9dbb62d) will decrease coverage by 0.88%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main     #181      +/-   ##
==========================================
- Coverage   39.96%   39.07%   -0.89%     
==========================================
  Files          44       45       +1     
  Lines        3218     3291      +73     
==========================================
  Hits         1286     1286              
- Misses       1683     1756      +73     
  Partials      249      249              

Impacted Files	Coverage Δ
cmd/provider/internal/client.go	0.00% <0.00%> (ø)
cmd/provider/internal/client_store.go	0.00% <0.00%> (ø)
cmd/provider/internal/entries_iter.go	0.00% <0.00%> (ø)
cmd/provider/internal/options.go	0.00% <0.00%> (ø)
cmd/provider/list.go	0.00% <0.00%> (ø)
cmd/provider/verify_ingest.go	0.00% <0.00%> (ø)

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