perf: Stop creating error before needing to throw

[FrederikBolding]

Stop creating Error and passing into assert, especially in hot paths as it takes a significant amount of time on mobile.

---

Note

Replaces assert(..., new Error(...)) with string messages in SnapController and Timer to avoid unnecessary Error construction.

• Performance refactor
  • packages/snaps-controllers/src/snaps/SnapController.ts
    • Use assert(condition, "message") instead of creating Error in getExpect, #createRollbackSnapshot (2 sites), and #getRuntimeExpect.
  • packages/snaps-controllers/src/snaps/Timer.ts
    • Same change in cancel, finish, pause, start, and resume.

^{Written by Cursor Bugbot for commit 8c15196. This will update automatically on new commits. Configure here.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.29%. Comparing base (93f69e5) to head (8c15196).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3664   +/-   ##
=======================================
  Coverage   98.29%   98.29%           
=======================================
  Files         417      417           
  Lines       11907    11907           
  Branches     1848     1848           
=======================================
  Hits        11704    11704           
  Misses        203      203           

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