feat: Add RawSigner trait to c2pa-crypto (derived from c2pa::Signer)

[scouten-adobe]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 80.74180% with 135 lines in your changes missing coverage. Please review.

Project coverage is 80.59%. Comparing base (2a65756) to head (1d9e7a8).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
sdk/src/cose_sign.rs	4.76%	40 Missing ⚠️
sdk/src/signer.rs	60.25%	31 Missing ⚠️
internal/crypto/src/raw_signature/signer.rs	77.38%	19 Missing ⚠️
internal/crypto/src/openssl/signers/rsa_signer.rs	86.13%	14 Missing ⚠️
sdk/src/utils/test_signer.rs	85.71%	11 Missing ⚠️
...nternal/crypto/src/openssl/signers/ecdsa_signer.rs	90.90%	6 Missing ⚠️
internal/crypto/src/p1363.rs	84.61%	6 Missing ⚠️
internal/crypto/src/openssl/cert_chain.rs	83.33%	3 Missing ⚠️
...ernal/crypto/src/openssl/signers/ed25519_signer.rs	94.00%	3 Missing ⚠️
sdk/src/utils/test.rs	50.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #716      +/-   ##
==========================================
- Coverage   80.71%   80.59%   -0.12%     
==========================================
  Files         117      117              
  Lines       31554    31540      -14     
==========================================
- Hits        25468    25420      -48     
- Misses       6086     6120      +34     

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[scouten-adobe]

Work in progress: I plan, as part of this PR, to move the signer implementations in to c2pa_crypto. This part moves most of the Signer trait into c2pa_crypto (here known as RawSigner, since it only implements the core signature algorithm).

More to come tomorrow …

[mauricefisher64]

Mandatory in 2.x

[mauricefisher64]

Approved.