chore: Enable sync CAWG validation

[gpeacock]

We currently will auto validate CAWG identity when the verify apis are called async, but not when they are called synchronously (it silently logs a warning and skips validation).

This allows cawg verification in sync calls by default. Identity validation can be disabled with a setting.

c_ffi no longer needs a tokio runtime to block on async validation.

[codspeed-hq]

Merging this PR will not alter performance

✅ 30 untouched benchmarks
⏩ 64 skipped benchmarks¹

---

_{Comparing gpeacock/cawg_sync (f451ff1) with main (d000b52)}

Footnotes

1. 64 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[codecov]

Codecov Report

❌ Patch coverage is 78.33333% with 39 lines in your changes missing coverage. Please review.
✅ Project coverage is 78.28%. Comparing base (3ce6250) to head (f451ff1).
⚠️ Report is 12 commits behind head on main.

Files with missing lines	Patch %	Lines
sdk/src/identity/x509/x509_signature_verifier.rs	6.25%	15 Missing ⚠️
...entity/claim_aggregation/ica_signature_verifier.rs	87.50%	7 Missing ⚠️
sdk/src/identity/identity_assertion/assertion.rs	86.95%	6 Missing ⚠️
.../identity_assertion/built_in_signature_verifier.rs	16.66%	5 Missing ⚠️
cli/src/main.rs	0.00%	4 Missing ⚠️
c2pa_c_ffi/src/c_api.rs	94.73%	1 Missing ⚠️
sdk/src/reader.rs	96.42%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##             main    #2120    +/-   ##
========================================
  Coverage   78.28%   78.28%            
========================================
  Files         177      177            
  Lines       45599    45735   +136     
========================================
+ Hits        35695    35805   +110     
- Misses       9904     9930    +26     

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[tmathern]

For even more improvements, please consider: #2152 (Other topic, other PR).

[scouten-adobe]

This looks really good. Thank you!