vm: refactor to avoid unsafe array iteration

[aduh95]

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines

[aduh95]

Benchmark CI: https://ci.nodejs.org/view/Node.js%20benchmark/job/benchmark-node-micro-benchmarks/869/ (queued, will 404 until it starts)

[aduh95]

No perf regression or improvement

                                                                    confidence improvement accuracy (*)    (**)   (***)
 vm/create-context.js n=100                                                        -1.06 %       ±8.00% ±10.65% ±13.88%
 vm/run-in-context.js withSigintListener=0 breakOnSigint=0 n=1                     -1.67 %       ±7.09%  ±9.43% ±12.27%
 vm/run-in-context.js withSigintListener=0 breakOnSigint=1 n=1                      2.73 %       ±7.58% ±10.11% ±13.21%
 vm/run-in-context.js withSigintListener=1 breakOnSigint=0 n=1                      1.23 %       ±6.48%  ±8.65% ±11.31%
 vm/run-in-context.js withSigintListener=1 breakOnSigint=1 n=1                     -2.97 %       ±4.42%  ±5.89%  ±7.66%
 vm/run-in-this-context.js withSigintListener=0 breakOnSigint=0 n=1                -2.35 %       ±5.64%  ±7.50%  ±9.77%
 vm/run-in-this-context.js withSigintListener=0 breakOnSigint=1 n=1                 5.30 %       ±6.35%  ±8.48% ±11.10%
 vm/run-in-this-context.js withSigintListener=1 breakOnSigint=0 n=1                 1.00 %       ±5.77%  ±7.69% ±10.03%
 vm/run-in-this-context.js withSigintListener=1 breakOnSigint=1 n=1                -3.33 %       ±4.76%  ±6.33%  ±8.24%

Be aware that when doing many comparisons the risk of a false-positive
result increases. In this case there are 9 comparisons, you can thus
expect the following amount of false-positive results:
  0.45 false positives, when considering a   5% risk acceptance (*, **, ***),
  0.09 false positives, when considering a   1% risk acceptance (**, ***),
  0.01 false positives, when considering a 0.1% risk acceptance (***)
++ mv output030121-121422.csv /w/bnch-comp

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/35486/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/35496/

[aduh95]

Landed in e70e793