setting content type metadata on all core to * commands (#13506)

# Description

All core `to *` set content type pipeline metadata. 

# User-Facing Changes
- For consistency, `from json` no longer sets the content type metadata

# Tests + Formatting
- 🟢 `toolkit fmt`
- 🟢 `toolkit clippy`
- 🟢 `toolkit test`
- 🟢 `toolkit test stdlib

crates/nu-cmd-lang/src/example_support.rs

@@ -72,7 +72,7 @@ pub fn check_example_input_and_output_types_match_command_signature(
     witnessed_type_transformations
 }
 
-fn eval_pipeline_without_terminal_expression(
+pub fn eval_pipeline_without_terminal_expression(
     src: &str,
     cwd: &std::path::Path,
     engine_state: &mut Box<EngineState>,