refactor: replace regular prints with prints to stderr for warnings

[imrn99]

I'll replace those of split_edge methods in another PR

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 13.63636% with 19 lines in your changes missing coverage. Please review.

Project coverage is 81.48%. Comparing base (1eb96db) to head (7bcc253).

Files with missing lines	Patch %	Lines
honeycomb-core/src/attributes/manager.rs	0.00%	10 Missing :warning:
honeycomb-core/src/attributes/collections.rs	25.00%	6 Missing :warning:
honeycomb-kernels/src/grisubal/model.rs	0.00%	3 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #192 +/- ## ========================================== - Coverage 81.51% 81.48% -0.04% ========================================== Files 36 36 Lines 5329 5331 +2 ========================================== Hits 4344 4344 - Misses 985 987 +2 ```

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