src: elide heap allocation in structured clone implementation

[addaleax]

Small perf improvement:

$ node benchmark/compare.js --runs 100 \
>   --old ./node-0da120f879 --new ./node \
>   --filter structured-clone misc > comparison.csv && \
>   npx node-benchmark-compare comparison.csv

[00:02:15|% 100| 1/1 files | 200/200 runs | 3/3 configs]: Done
                                                    confidence improvement accuracy (*)   (**)  (***)
misc/structured-clone.js n=10000 type='arraybuffer'         **      1.81 %       ±1.28% ±1.68% ±2.16%
misc/structured-clone.js n=10000 type='object'               *      0.62 %       ±0.55% ±0.73% ±0.93%
misc/structured-clone.js n=10000 type='string'             ***      8.30 %       ±1.46% ±1.92% ±2.47%

Be aware that when doing many comparisons the risk of a false-positive result increases.
In this case, there are 3 comparisons, you can thus expect the following amount of false-positive results:
  0.15 false positives, when considering a   5% risk acceptance (*, **, ***),
  0.03 false positives, when considering a   1% risk acceptance (**, ***),
  0.00 false positives, when considering a 0.1% risk acceptance (***)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.74%. Comparing base (ae2ffce) to head (8846c7a).
⚠️ Report is 7 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #61703      +/-   ##
==========================================
- Coverage   89.75%   89.74%   -0.02%     
==========================================
  Files         674      674              
  Lines      204416   204416              
  Branches    39285    39283       -2     
==========================================
- Hits       183472   183450      -22     
- Misses      13227    13263      +36     
+ Partials     7717     7703      -14     

Files with missing lines	Coverage Δ
src/node_messaging.cc	82.18% <100.00%> (-0.71%)	⬇️

... and 30 files with indirect coverage changes

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[anonrig]

Elegant.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/71221/