run_in_environment panics on Zsh, Fish, PowerShell, NuShell, Xonsh

### Checklist - [x] I added a descriptive title - [x] I searched open reports and couldn't find a duplicate ### What happened? rattler_shell::run::run_in_environment (used by pixi) panics with unimplemented! for any shell other than Bash or CmdExe. Users running Zsh, Fish, PowerShell, NuShell, or Xonsh will see a crash at runtime. All 7 ShellEnum variants need to be handled. @baszalmstra what do you think ? ### Additional Context _No response_