Additional fix for CVE-2024-53899: substitute the activation script
placeholders in one pass, so a placeholder name inside a path cannot break
the quoting
Additional fix for CVE-2024-53899: keep the environment name from running
as a command from the shell prompt in bash, POSIX-mode bash and zsh
Additional fix for CVE-2024-53899: quote the activate.fish values for fish,
so a backslash before a quote cannot end the literal