errors: provide defaults for unmapped uv errors

[cjihrig]

libuv does not map 100% of errors. When an unmapped error is encountered, the Map returns undefined, which is then unsuccessfully destructured, causing an exception. This commit adds a default value in the event of an unmapped error.

A test will be added once #29285 lands.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• commit message follows commit guidelines

[bnoordhuis]

LGTM but note there's another lazyErrmapGet() in lib/internal/util.js because of course there is.

That one handles missing entries by returning Unknown system error ${err}. That's arguably a little nicer for debugging.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/25235/

[cjihrig]

LGTM but note there's another lazyErrmapGet() in lib/internal/util.js because of course there is.

That one is gone, as of #29285.

That one handles missing entries by returning Unknown system error ${err}. That's arguably a little nicer for debugging.

I've updated the PR so that uvException() and uvExceptionWithHostPort() in lib/internal/errors.js now handle undefined being returned from uvErrmapGet(). So, getSystemErrorName() in lib/internal/util.js won't be impacted by this change at all.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/25268/

EDIT: CI was yellow.

[Trott]

Landed in c246f81