Update to latest pinning API

[Thomasdezeeuw]

PR rust-lang/rust#53877 change the pinning API, breaking futures as well. Is someone working on fixing this? Or should I make an attempt?

[cramertj]

I was planning to wait on this until rust-lang/rust#54339 landed, which includes more breaking changes.

[JesseWright]

@cramertj I believe this can be closed now that #1268 and #1273 have been merged and #1266 closed.