Avoid using shellcode env with pkgx

[waliid]

Description

This PR fixes an issue with pkgx. Indeed, since there is no longer shellcode env support in pkgx, some of our scripts were failing.

Shellcode

The pkgx suite has had its scopes tightened. There is no shellcode in pkgx
anymore.

Changes made

• Use pkgx directly instead of using shellcode env.

Checklist

• APIs have been properly documented (if relevant).
• The documentation has been updated (if relevant).
• New unit tests have been written (if relevant).
• The demo has been updated (if relevant).