Summary:
`tempdir` has been deprecated since 2018:
https://github.com/rust-lang-deprecated/tempdir/pull/46
It's functionality was merged into `tempfile` with minor tweaks:
- Methods names: `new` -> `with_prefix`, `new_in` -> `with_prefix_in`.
- `with_prefix_in`'s args order is reversed.
- Temp dirs no longer have a period between the prefix and the random
name (before `foo.123abc`, now `foo123abc`).
Reviewed By: shayne-fletcher
Differential Revision: D50526255
fbshipit-source-id: bdb3b53a6b09a09c70c8e2533ad2cea46ee2842b
baf9d9ab37