lib: remove unused join from internal/util

[anonrig]

                                                                      confidence improvement accuracy (*)    (**)   (***)
util/inspect-array.js type='denseArray' len=100000 n=500                             -0.78 %       ±5.48%  ±7.29%  ±9.49%
util/inspect-array.js type='denseArray' len=100 n=500                                -5.15 %       ±5.50%  ±7.32%  ±9.53%
util/inspect-array.js type='denseArray_showHidden' len=100000 n=500            *     -8.22 %       ±8.18% ±10.95% ±14.38%
util/inspect-array.js type='denseArray_showHidden' len=100 n=500                     -3.31 %       ±6.25%  ±8.31% ±10.82%
util/inspect-array.js type='mixedArray' len=100000 n=500                              0.28 %       ±3.15%  ±4.20%  ±5.47%
util/inspect-array.js type='mixedArray' len=100 n=500                                -0.59 %       ±5.78%  ±7.69% ±10.01%
util/inspect-array.js type='sparseArray' len=100000 n=500                             0.47 %       ±5.83%  ±7.75% ±10.09%
util/inspect-array.js type='sparseArray' len=100 n=500                               -2.40 %       ±5.77%  ±7.69% ±10.04%
util/inspect.js option='colors' method='Array' n=20000                        **     -5.78 %       ±4.28%  ±5.71%  ±7.46%
util/inspect.js option='colors' method='Date' n=20000                                -1.20 %       ±5.08%  ±6.76%  ±8.80%
util/inspect.js option='colors' method='Error' n=20000                                0.09 %       ±3.66%  ±4.88%  ±6.37%
util/inspect.js option='colors' method='Number' n=20000                               3.77 %       ±4.35%  ±5.82%  ±7.65%
util/inspect.js option='colors' method='Object_deep_ln' n=20000              ***     -3.91 %       ±1.73%  ±2.30%  ±3.00%
util/inspect.js option='colors' method='Object_empty' n=20000                        -2.67 %       ±6.67%  ±8.89% ±11.61%
util/inspect.js option='colors' method='Object' n=20000                               1.86 %       ±4.28%  ±5.69%  ±7.41%
util/inspect.js option='colors' method='Set' n=20000                                 -1.61 %       ±5.51%  ±7.34%  ±9.55%
util/inspect.js option='colors' method='String_boxed' n=20000                        -0.50 %       ±4.42%  ±5.89%  ±7.66%
util/inspect.js option='colors' method='String_complex' n=20000                       3.23 %       ±6.30%  ±8.39% ±10.94%
util/inspect.js option='colors' method='String' n=20000                               1.63 %       ±6.97%  ±9.27% ±12.07%
util/inspect.js option='colors' method='TypedArray_extra' n=20000             **     -4.70 %       ±3.24%  ±4.31%  ±5.62%
util/inspect.js option='colors' method='TypedArray' n=20000                          -3.87 %       ±5.63%  ±7.50%  ±9.76%
util/inspect.js option='none' method='Array' n=20000                                 -0.92 %       ±3.96%  ±5.32%  ±7.03%
util/inspect.js option='none' method='Date' n=20000                                   2.51 %       ±6.50%  ±8.66% ±11.28%
util/inspect.js option='none' method='Error' n=20000                                  2.96 %       ±6.10%  ±8.11% ±10.56%
util/inspect.js option='none' method='Number' n=20000                                 5.64 %       ±5.74%  ±7.65%  ±9.99%
util/inspect.js option='none' method='Object_deep_ln' n=20000                ***     -8.47 %       ±2.50%  ±3.34%  ±4.36%
util/inspect.js option='none' method='Object_empty' n=20000                          -2.30 %       ±4.93%  ±6.57%  ±8.59%
util/inspect.js option='none' method='Object' n=20000                                -1.26 %       ±5.20%  ±6.92%  ±9.01%
util/inspect.js option='none' method='Set' n=20000                                    1.01 %       ±5.69%  ±7.59%  ±9.92%
util/inspect.js option='none' method='String_boxed' n=20000                          -0.80 %       ±6.16%  ±8.20% ±10.67%
util/inspect.js option='none' method='String_complex' n=20000                        -4.49 %       ±7.04%  ±9.39% ±12.26%
util/inspect.js option='none' method='String' n=20000                                -2.29 %       ±6.22%  ±8.27% ±10.77%
util/inspect.js option='none' method='TypedArray_extra' n=20000              ***    -13.83 %       ±5.95%  ±7.93% ±10.33%
util/inspect.js option='none' method='TypedArray' n=20000                     **     -6.98 %       ±4.39%  ±5.86%  ±7.68%
util/inspect.js option='showHidden' method='Array' n=20000                   ***     -4.50 %       ±2.25%  ±3.00%  ±3.92%
util/inspect.js option='showHidden' method='Date' n=20000                             1.88 %       ±5.78%  ±7.69% ±10.01%
util/inspect.js option='showHidden' method='Error' n=20000                           -1.39 %       ±2.65%  ±3.53%  ±4.60%
util/inspect.js option='showHidden' method='Number' n=20000                           1.78 %       ±5.11%  ±6.81%  ±8.87%
util/inspect.js option='showHidden' method='Object_deep_ln' n=20000          ***     -8.52 %       ±2.52%  ±3.36%  ±4.39%
util/inspect.js option='showHidden' method='Object_empty' n=20000                    -0.56 %       ±5.49%  ±7.31%  ±9.53%
util/inspect.js option='showHidden' method='Object' n=20000                          -0.50 %       ±4.96%  ±6.60%  ±8.60%
util/inspect.js option='showHidden' method='Set' n=20000                             -3.85 %       ±5.54%  ±7.37%  ±9.59%
util/inspect.js option='showHidden' method='String_boxed' n=20000              *     -4.81 %       ±4.17%  ±5.55%  ±7.23%
util/inspect.js option='showHidden' method='String_complex' n=20000                   0.13 %       ±6.03%  ±8.02% ±10.44%
util/inspect.js option='showHidden' method='String' n=20000                          -0.24 %       ±4.77%  ±6.35%  ±8.27%
util/inspect.js option='showHidden' method='TypedArray_extra' n=20000        ***    -12.24 %       ±2.16%  ±2.88%  ±3.75%
util/inspect.js option='showHidden' method='TypedArray' n=20000              ***    -16.48 %       ±2.03%  ±2.72%  ±3.56%
util/inspect-proxy.js isProxy=0 showProxy=0 n=100000                          **     -2.96 %       ±1.82%  ±2.43%  ±3.16%
util/inspect-proxy.js isProxy=0 showProxy=1 n=100000                         ***     -3.45 %       ±1.81%  ±2.40%  ±3.13%
util/inspect-proxy.js isProxy=1 showProxy=0 n=100000                         ***     -3.93 %       ±2.26%  ±3.00%  ±3.91%
util/inspect-proxy.js isProxy=1 showProxy=1 n=100000                         ***     -6.00 %       ±2.62%  ±3.50%  ±4.58%

[cjihrig]

LGTM if the CI passes.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/48140/

[anonrig]

Benchmark CI: https://ci.nodejs.org/view/Node.js%20benchmark/job/benchmark-node-micro-benchmarks/1239/

[anonrig]

It seems. Array.prototype.join is still super slow. But, how, why?