perf: fast array copy for installed transformers

[KnorpelSenf]

V8 is fairly optimized for [...arr] and my benchmarks only show a few nanoseconds of improvement for Deno, regardless of the size of the array. However, in general, creating an iterator over an array, traversing all elements on it, and pushing them onto a new array will be slower than a slice call. Since grammY runs in more environments, we can expect greater improvements elsewhere.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 47.74%. Comparing base (a104c42) to head (e87ba8b).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #596      +/-   ##
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- Coverage   47.86%   47.74%   -0.13%     
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  Files          19       19              
  Lines        6159     6177      +18     
  Branches      343      343              
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+ Hits         2948     2949       +1     
- Misses       3207     3224      +17     
  Partials        4        4              

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