move create_default_context out of cli.rs and into its own mod (#2833)

crates/nu-cli/src/commands.rs

@@ -30,6 +30,7 @@ pub(crate) mod date;
 pub(crate) mod debug;
 pub(crate) mod def;
 pub(crate) mod default;
+pub(crate) mod default_context;
 pub(crate) mod describe;
 pub(crate) mod do_;
 pub(crate) mod drop;