Sometimes Bun.spawn calls the onExit callback before the Bun.spawn() callback is called.
Instead of delaying a tick, we set the `Subprocess` to be the first argument to the `onExit` callback now.
* fix(stream): get Duplex working
* feat(process): add stdin,stdout,stderr in a semi-broken state (pipes??)
* test(NodeTestHelpers): fix test names
* test(NodeTestHelpers): add test for createDoneDotAll done called w error
* test(NodeTestHelpers): remove stray console.log
* fix(stream): fix bug in Duplex, Readable
* test(process.stdio): rename test
* fix(process.stdio): change onData listener to onReadable
* refactor(streams): add file-wide debug fn, destructure opts
* fix(child_process): check isCallable on promise
* fix: get stdio streams mostly working (mostly)
* fix(child_process): wait until stream is drained before calling end?
* fix(child_process): change to result?.then
* debug(child_process,streams): add EE id tracking, add shim for stdio after handle is dead
* test(child_process): fix double pipe test, temp fix for ChildProcess.kill() return val
* fix(child_process): remove immediate emit of exit on kill
* debug(streams): add more debug log
* debug(streams): add more debug logs part 2
* feat(streams,fs): add NativeWritable, adapt fs.WriteStream and fs.ReadStream to native
This matches Deno's behavior (get() combines, iterator preserves the order, set and append combine), but implements both the Cloudflare Workers `getAll()` and the potential standard `getSetCookie` function. The rationale for choosing both is to better support libraries which check for `getAll` and also because `getSetCookie` seems a little confusing (names are hard)
This also makes `.toJSON` and JSON.stringify return an array for `Set-Cookie`
