Clean up and unify the use of tempdir and tempfile

[yihuaf]

Currently, we are rolling our own implementation of tempdir and duplicated the code in multiple places. In addition, I don't like the struct implements using option<path> and the path() has a expect() which can panic if called after remove. The proposed solution is to use tempfile crate. https://github.com/Stebalien/tempfile

• libcontainer Migrate to tempfile for libcontainer and youki crate #1887
• youki Migrate to tempfile for libcontainer and youki crate #1887
• integration test Migrate integration test to use tempfile #1891
• libcgroup replaced tempdir in libcgroup #1888

[utam0k]

👍