What's the problem this PR addresses?

We don't support path Buffers in @yarnpkg/fslib.

Fixes #1818.

Supersedes:

• Resolves feat(fslib): path buffer and file url support #1584.
• Resolves fix(fslib): ensure path is a string before calling replace(). #4215.
• Resolves fix(fslib): handle file path buffers #4907.
• Resolves Support Buffers in toPortablePath #4914.

How did you fix it?

Renamed URLFS to NodePathFS and implemented support for mapping Buffers to strings.

We currently only support valid utf8 buffers because binary buffers cannot be supported without keeping the paths as buffers until the end (see #4907 (comment)).

Because of this, we now throw an error when encountering buffers that cannot be encoded as utf8 and encourage users to upvote this issue so that we can gather how common non-utf8 buffers are.

The check uses Buffer.byteLength (credit to @arcanis for coming up with this idea) instead of Buffer.compare since the latter is quite slower.

Checklist

• I have read the Contributing Guide.

• I have set the packages that need to be released for my changes to be effective.

• I will check that all automated PR checks pass before the PR gets reviewed.