os: fix Process struct fields documentation applied to wrong field

[bramvbilsen]

The fields of the Process struct in the os modules incorrectly have their documentation behind the field, instead of before. Example of what it currently looks like:

pub struct Process {
pub mut:
        // ...
	pid      int    // the PID of the process
	code     int = -1
	// the exit code of the process, != -1 *only* when status is .exited *and* the process was not aborted
	// ...
}

This results in code incorrectly having the documentation associated with pid. This specific case is confusing in particular as both are integers and code could be mistaken for the pid after reading the associated comments.