Mark `t.i.process.Process` and `t.i.process.PTYProcess` as implementing IProcessTransport
|Reported by:||Screwtape||Owned by:|
branch-diff, diff-cov, branch-cov, buildbot
Currently the IProcessTransport documentation claims that the only process transport in Twisted is for Win32, which is a total lie. t.i.process.Process and t.i.process.PTYProcess also implement it, and are very likely much more solid implementations.
We should mark both those classes as implementing that interface.
(this was filed once before as #4479, but that ticket got derailed into a different documentation issue)