add -e flag to print, to print the value to stderr (#5935)

* Refactor: make stdout write all and flush as generic function

* support print to stderr

crates/nu-command/tests/commands/mod.rs

@@ -44,6 +44,7 @@ mod open;
 mod parse;
 mod path;
 mod prepend;
+mod print;
 #[cfg(feature = "database")]
 mod query;
 mod random;