security: fix CVE-2022-41716 [1.18 backport]

[gopherbot]

@neild requested issue #56284 to be considered for backport to the next 1.18 minor release.

@gopherbot please open backport issues

(Sorry, I keep getting the process on this wrong. This issue is for the fix, backport issues for upcoming minor releases.)

[gopherbot]

Change https://go.dev/cl/446915 mentions this issue: [release-branch.go1.18] syscall, os/exec: reject environment variables containing NULs

[gopherbot]

Closed by merging aba57b0 to release-branch.go1.18.