[ptysvc] Rewrite in rust

Change-Id: Ie61f0f29ffd81d49e0e0bd278ae3baea6a6a6964
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1468074
Commit-Queue: Suraj Malhotra <surajmalhotra@google.com>
Fuchsia-Auto-Submit: Suraj Malhotra <surajmalhotra@google.com>
Reviewed-by: Bruno Dal Bo <brunodalbo@google.com>
13 files changed