chore: Use SHA-256 utility

[FrederikBolding]

Use sha256 utility for checksumming. The utility matches the existing implementation and was upstreamed to utils.

---

Note

Switches snaps-utils checksumming to the shared sha256 from @metamask/utils and cleans up related dependencies/tests.

• Update checksum to call @metamask/utils sha256; checksumFiles unchanged except for using the new helper
• Remove conditional WebCrypto/noble logic and corresponding tests in checksum.test.ts
• Drop @noble/hashes from package.json and yarn.lock

^{Written by Cursor Bugbot for commit 02cf92d. This will update automatically on new commits. Configure here.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.34%. Comparing base (1fdd521) to head (02cf92d).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3781      +/-   ##
==========================================
- Coverage   98.34%   98.34%   -0.01%     
==========================================
  Files         422      422              
  Lines       12066    12059       -7     
  Branches     1876     1872       -4     
==========================================
- Hits        11866    11859       -7     
  Misses        200      200              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.