refactor!: Use hash private functions for updating internals

[FrederikBolding]

The updateSnap, processRequestedSnap and authorize do not need to be part of the public API and it makes maintaining them much simpler if they aren't. This PR makes them all hash private and modifies tests to use the installSnaps public API instead. This is also what is used in production for all updating of Snaps.

Since these functions are guaranteed to be called only internally, this PR also removes some dead code that was no longer needed.

This effort was moved out of the OTA branch to simplify review but does contain breaking changes, namely the above functions no longer being callable.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.28%. Comparing base (bd2ad5d) to head (3991ee5).
⚠️ Report is 13 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3601      +/-   ##
==========================================
- Coverage   98.28%   98.28%   -0.01%     
==========================================
  Files         417      417              
  Lines       11771    11763       -8     
  Branches     1832     1828       -4     
==========================================
- Hits        11569    11561       -8     
  Misses        202      202              

☔ 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.