Add vscode.workspace.fs.mkdirp().

[ericsnowcurrently]

(see #84175)

For the Python extension, we had been using fs-extra's mkdirp(), though we could have used node's mkdir() with the recursive: true option. T he new filesystem API provides createDirectory(), but that fails if the parent directory is missing. So we wrote a wrapper around that. However, it isn't an obvious solution, so it would be nice if the extension provided the equivalent of mkdirp().

@jrieken

[jrieken]

fs.createDirectory does this, I will update the docs

[ericsnowcurrently]

Thanks, @jrieken! Yeah, the docs basically say the exact opposite. :)