querystring stringify/parse is inconsistent and does not roundtrip

[ChALkeR]

> querystring.stringify({ foo: "a\ud802" })
Uncaught URIError [ERR_INVALID_URI]: URI malformed // correct
> querystring.stringify({ foo: "a\ud802b" })
'foo=a%F0%90%A1%A2' // incorrect
> encodeURIComponent("a\ud802b")
Uncaught URIError: URI malformed // correct
> foo = "a\ud802b"; querystring.parse(querystring.stringify({ foo })).foo === foo
false // does not roundtrip

I would argue that "a\ud802b" was supposed to throw, as querystring.stringify is already throwing on some non-well-formed strings, it just misses some

See also anonrig/fast-querystring#92

This was autodetected by the scanner behind https://github.com/deepview-autofix

For anyone remembering querystring being moved to Legacy: https://nodejs.org/api/querystring.html has been updated from Legacy to Stable, and is currently labeled Stable in the docs, see #44912

[ChALkeR]

cc @mcollina and @anonrig as people interacting with querystring, wdyt should happen here?

[mcollina]

I would recommend fixing. The standard-based alternative is so much slower that this is important to keep in core.