perf: Stop validating JSON for stored state

[FrederikBolding]

Removes some validation checks when storing and retrieving state from snap_manageState. Since we have input sanitization on the Snap side, we can improve performance significantly when retrieving state by parsing it without additional validation.

Also improves performance slightly by not using isVaultUpdated as the sole check for caching (as that function can be somewhat expensive to call).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.46%. Comparing base (2c5a1e5) to head (81776df).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2845   +/-   ##
=======================================
  Coverage   94.46%   94.46%           
=======================================
  Files         486      486           
  Lines       10358    10360    +2     
  Branches     1579     1582    +3     
=======================================
+ Hits         9785     9787    +2     
  Misses        573      573           

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