Error printing changes for watch (#5389)

* Move CliError to nu-protocol

clean up comment

* Enable printing errors instead of just returning them

* Nicer Miette error printing in watch command

crates/nu-protocol/src/lib.rs

@@ -1,4 +1,5 @@
 pub mod ast;
+mod cli_error;
 mod config;
 pub mod engine;
 mod example;
@@ -14,6 +15,7 @@ mod ty;
 mod value;
 mod variable;
 
+pub use cli_error::*;
 pub use config::*;
 pub use engine::{ENV_VARIABLE_ID, IN_VARIABLE_ID, NU_VARIABLE_ID};
 pub use example::*;