Polynomial: differentiate & print methods.

[feltroidprime]

Rationale :

• differentiate can be useful

• printing nicely the poly as well

• Will enable drop-in replacement in Garaga for the Polynomial struct.

Thank you! :)

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 96.42857% with 2 lines in your changes missing coverage. Please review.

Project coverage is 71.12%. Comparing base (e14cf2b) to head (cae0f12).

Files with missing lines	Patch %	Lines
math/src/polynomial/mod.rs	96.42%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #929 +/- ## ========================================== + Coverage 71.08% 71.12% +0.04% ========================================== Files 144 144 Lines 31824 31880 +56 ========================================== + Hits 22622 22676 +54 - Misses 9202 9204 +2 ```

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