Tezt: Keep the standard input of daemons

Context

This can for instance be used to send commands to a “daemon” through the standard input. One potential use case could be to “daemonize” the WASM debugger and have scenarios run with it. But any binary that can receive commands from stdin can benefit from this simple, “free” change (considering Process.spawn is calling Process.spawn_with_stdin only to “forget” about the out channel).

Manually testing the MR

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR