fix: update codebase to work with Deno RC

[iuioiua]

• We'll need to re-enable Codecov as soon as fix(coverage): ignore urls from doc testing deno#25736 is merged.
• The new deno test --doc functionality is great! We've fixed a bunch of snippets with it. Well done, @magurotuna!
• Most line changes are a result of snippet evaluation now being handled by deno test --doc.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.28%. Comparing base (6a4eb6c) to head (1240773).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6018   +/-   ##
=======================================
  Coverage   96.28%   96.28%           
=======================================
  Files         496      496           
  Lines       39605    39606    +1     
  Branches     5841     5840    -1     
=======================================
+ Hits        38134    38135    +1     
  Misses       1429     1429           
  Partials       42       42           

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[iuioiua]

This is blocked on denoland/deno#25732