fs.cpSync / fs.cp / fs.promises.cp fails when src/dest args are Buffer

### Version All ### Platform ```text All ``` ### Subsystem fs ### What steps will reproduce the bug? ``` const { cpSync, cp, promises } = require('node:fs'); cpSync(Buffer.from('dirA'), Buffer.from('dirB'), { recursive: true, filter(...args) { console.log(...args); return true; } }); // throws cp(Buffer.from('dirA'), Buffer.from('dirB'), { recursive: true, filter(...args) { console.log(...args); return true; } }, (err) => { console.log(err); // errors }); promises.cp(Buffer.from('dirA'), Buffer.from('dirB'), { recursive: true, filter(...args) { console.log(...args); return true; } }); // rejects ``` ### How often does it reproduce? Is there a required condition? Always ### What is the expected behavior? Why is that the expected behavior? It should just work without throwing. The filter function should be called with the option to receive the path as either a string, Buffer, or URL. ### What do you see instead? It throws. ### Additional information The issue here is that the underlying implementation assumes that the paths are strings and tries to use the path.join function to concatenate them, which obviously does not work for Buffer and URL. The implementation has to be able to support Buffer and URL paths in order to properly support arbitrary text encodings in file names etc. Unfortunately, because of the way the callback is designed, it's not clear that there is an immediate non-breaking fix ready available. @dario-piotrowicz @cjihrig @anonrig