Add ppid to ps command (#8750)

# Description

Adds the `ppid` field that's available on all supported platforms to the
`ps` command. This would be useful in my scripts.

# User-Facing Changes

- ps output now contains an extra column

# Tests + Formatting

Not sure if I need to add a test for this

# After Submitting

Update https://www.nushell.sh/book/quick_tour.html#quick-tour to show
the new table

crates/nu-command/src/system/ps.rs

@@ -86,6 +86,12 @@ fn run_ps(engine_state: &EngineState, call: &Call) -> Result<PipelineData, Shell
             span,
         });
 
+        cols.push("ppid".to_string());
+        vals.push(Value::Int {
+            val: proc.ppid() as i64,
+            span,
+        });
+
         cols.push("name".to_string());
         vals.push(Value::String {
             val: proc.name(),