Add encodeEntities fast path for inputs that don't need anything replaced

[jviide]

This pull request attempts to optimize util.js's encodeEntities function. This happens by skipping the .replace(...) chain for inputs that contain no characters that should be replaced.

The benchmarks seem get a boost from this (Node v14.16.0, Linux, x86), especially the SearchResults one. Here are the npm run bench results before this change:

Text:
baseline x 80.883 ops/sec ±1.16 (67 runs sampled)
current x 94.593 ops/sec ±2.36 (73 runs sampled)

SearchResults:
baseline x 404.532 ops/sec ±2.42 (79 runs sampled)
current x 448.104 ops/sec ±2.61 (83 runs sampled)

And after this change:

Text:
baseline x 83.055 ops/sec ±1.54 (68 runs sampled)
current x 103.134 ops/sec ±1.95 (74 runs sampled)

SearchResults:
baseline x 453.03 ops/sec ±2.13 (84 runs sampled)
current x 648.997 ops/sec ±2.88 (83 runs sampled)

[andrewiggins]

Niceee!!

[marvinhagemeister]

Sweet 🙌