url: encode null character at the end of file path

[EarlyRiser42]

Fixes: #51167

Description

To maintain current performance while addressing the whitespace trimming issue, I opted to pre-encode the pathname. Modifying the URL parse function would require more extensive changes, so pre-encoding is a simpler solution.

Test

import { pathToFileURL } from 'url';

const filename = `test-${String.fromCharCode(0)}`;
console.log(pathToFileURL(filename).toString()); // file:///[...]/test-%00

Previously, this would output test-, but now it correctly outputs file:///[...]/test-%00.

Benchmark

                                                                                                                 confidence improvement accuracy (*)   (**)  (***)
url/whatwg-url-to-and-from-path.js n=5000000 method='fileURLToPath' input='file:///dev/null?key=param&bool'                      0.53 %       ±0.89% ±1.20% ±1.58%
url/whatwg-url-to-and-from-path.js n=5000000 method='fileURLToPath' input='file:///dev/null?key=param&bool#hash'                -0.23 %       ±0.86% ±1.16% ±1.53%
url/whatwg-url-to-and-from-path.js n=5000000 method='fileURLToPath' input='file:///dev/null'                                    -0.56 %       ±1.33% ±1.76% ±2.30%
url/whatwg-url-to-and-from-path.js n=5000000 method='pathToFileURL' input='file:///dev/null?key=param&bool'                      0.42 %       ±1.12% ±1.50% ±1.98%
url/whatwg-url-to-and-from-path.js n=5000000 method='pathToFileURL' input='file:///dev/null?key=param&bool#hash'         **     -0.87 %       ±0.60% ±0.79% ±1.03%
url/whatwg-url-to-and-from-path.js n=5000000 method='pathToFileURL' input='file:///dev/null'                                    -0.50 %       ±1.50% ±1.99% ±2.60%

Be aware that when doing many comparisons the risk of a false-positive result increases.
In this case, there are 6 comparisons, you can thus expect the following amount of false-positive results:
  0.30 false positives, when considering a   5% risk acceptance (*, **, ***),
  0.06 false positives, when considering a   1% risk acceptance (**, ***),
  0.01 false positives, when considering a 0.1% risk acceptance (***)

The local benchmark doesn't show a statistically significant performance degradation

[nodejs-github-bot]

Review requested:

• @nodejs/url

[EarlyRiser42]

@RedYetiDev
Hello sir,

If you don't mind, could you please review my PR? I saw that you have reviewed PRs associated with URL files before, so I thought you might be able to help. If this is a mistake, I apologize for the inconvenience.

[RedYetiDev]

Hi! I'm a member of the triage team, so I help to perform basic reviews and labelings of issues and PRs. I don't know too much of the context of null character encoding, but seeing as no tests fail, and little perf impact, this does look good to me. Keep in mind that my opinion doesn't hold much "weight" in the actual review process.

[EarlyRiser42]

Thank you for your kind review, sir. I don't want to bother the Node.js team, but it's been more than a week since I submitted this PR, and I was concerned it might have been overlooked. That's why I mentioned you. I will wait a bit longer and then find someone who can approve my PR. Thank you so much for your attention and help. I truly appreciate it.