Rollup merge of #141832 - workingjubilee:explain-what-toctou-races-are, r=thomcc,ChrisDenton

library: explain TOCTOU races in `fs::remove_dir_all`

In the previous description it said there was a TOCTOU race but did not explain exactly what the problem was. I sat down with the CVE, reviewed its text, and created this explanation. This context should hopefully help people understand the actual risk as-such.

Incidentally, it also fixes the capitalization on the name of Redox OS.

Original CVE and advisory:
- CVE: https://www.cve.org/CVERecord?id=CVE-2022-21658
- security advisory: https://groups.google.com/g/rustlang-security-announcements/c/R1fZFDhnJVQ?pli=1
- github cross-post: GHSA-r9cc-f5pr-p3j2

Author: jhpratt