feat(crypto): Make box_size parameter on c2pa_crypto::cose::sign an Option

[scouten-adobe]

Signing via CAWG identity SDK for X.509 credentials does the padding at a different stage so I need to disable it here.

[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 78.67%. Comparing base (06c57a5) to head (db0f586).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/crypto/src/cose/sign.rs	62.50%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #879      +/-   ##
==========================================
- Coverage   78.67%   78.67%   -0.01%     
==========================================
  Files         139      139              
  Lines       32120    32122       +2     
==========================================
  Hits        25271    25271              
- Misses       6849     6851       +2     

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[gpeacock]

I thought you weren't a fan of Option parameters ;) I believe we still have copies of the cose signers in the c2pa-rs sdk. Perhaps it is time to just remove those, since a user could call the crypto versions directly. I'm not sure how that would impact our signer though.

[scouten-adobe]

@gpeacock I've stripped away some of those signers for common test cases, but some remain because the c2pa::Signer interface has things that aren't in (and shouldn't be in) the RawSigner interface.