Implement PTY to handle both stdout, stderr with redirects

[heaths]

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[heaths]

Doesn't work on Windows because it uses AsFd et. al. for nix. This definitely indicates that to solve #29 I'll need to write my own, which also gives me an opportunity to split (perhaps tag like the current HEAD at this time?) stdout and stderr.

[heaths]

I may need to fork the project or just start anew. Their repo site is giving an HTTP 502.

In any case, the question remains how to:

1. Maintain any VT color sequences written by the child process.
2. Split stdout, stderr according to what the user specified e.g., akv run -- child_proc 2> /dev/null.
3. Mask any retrieved secrets in both stdout, stderr.

Considering https://www.man7.org/linux/man-pages/man3/forkpty.3.html and a .NET project I found at https://github.com/microsoft/vs-pty.net, maybe I'm overthinking this. If I start a process under a PTY, I don't need to actually handle stdout and stderr separately. I mask any secrets found regardless. So something like https://docs.rs/pty-process/0.5.1/pty_process/blocking/struct.Command.html or equivalent on Windows should work.

[heaths]

This does actually work - well, almost. I still can't redirect stdout and/or stderr like I can with op, but perhaps if I wrap the stdout and stderr readers from pty-process in something that can "tag" them I could. I would "forward" the file descriptor check that isatty uses; though, IIRC, it's the FD that the command writes to directly so I don't know if that'll work.

Works:

op run -- target/release/examples/printenv 2> /dev/null

Doesn't work (doesn't redirect):

akv run -- target/release/examples/printenv 2> /dev/null

[heaths]

Got this working with my own PTY implementation. Properly detects and shows colors, properly interleaves, and properly redirects stdout and/or stderr.