gh-87868: Sort and remove duplicates in getenvironment() (GH-102731) Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com> Co-authored-by: Pieter Eendebak <pieter.eendebak@gmail.com> Co-authored-by: Erlend E. Aasland <erlend.aasland@protonmail.com>