Add metadata on open --raw with bytestreams (#14141)

# Description

This PR closes #14137 and allows the display hook to be set on byte
streams. So, with a hook like this below.
```nushell
display_output: {
    metadata access {|meta| match $meta.content_type? {
        "application/x-nuscript" | "application/x-nuon" | "text/x-nushell" => { nu-highlight },
        "application/json" => { ^bat --language=json --color=always --style=plain --paging=never },
        _ => {},
        }
    } | table
}
```
You could type `open toolkit.nu` and the text of toolkit.nu would be
highlighted by nu-highlight. This PR also changes the way content-type
is assigned with `open`. Previously it would only assign it if `--raw`
was specified.

Lastly, it changes the `is_external()` function to only say
`ByteStreamSource::Child`'s are external instead of both Child and
`ByteStreamSource::File`. Again, this was to allow the hook to function
properly. I'm not sure what negative ramifications changing
`is_external()` could have, but there may be some?

# User-Facing Changes
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# Tests + Formatting
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> **Note**
> from `nushell` you can also use the `toolkit` as follows
> ```bash
> use toolkit.nu # or use an `env_change` hook to activate it
automatically
> toolkit check pr
> ```
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crates/nu-cli/src/util.rs

@@ -282,8 +282,22 @@ fn evaluate_source(
     }?;
 
     if let PipelineData::ByteStream(..) = pipeline {
-        pipeline.print(engine_state, stack, false, false)
-    } else if let Some(hook) = engine_state.get_config().hooks.display_output.clone() {
+        // run the display hook on bytestreams too
+        run_display_hook(engine_state, stack, pipeline, false)
+    } else {
+        run_display_hook(engine_state, stack, pipeline, true)
+    }?;
+
+    Ok(false)
+}
+
+fn run_display_hook(
+    engine_state: &mut EngineState,
+    stack: &mut Stack,
+    pipeline: PipelineData,
+    no_newline: bool,
+) -> Result<(), ShellError> {
+    if let Some(hook) = engine_state.get_config().hooks.display_output.clone() {
         let pipeline = eval_hook(
             engine_state,
             stack,
@@ -292,14 +306,11 @@ fn evaluate_source(
             &hook,
             "display_output",
         )?;
-        pipeline.print(engine_state, stack, false, false)
+        pipeline.print(engine_state, stack, no_newline, false)
     } else {
-        pipeline.print(engine_state, stack, true, false)
-    }?;
-
-    Ok(false)
+        pipeline.print(engine_state, stack, no_newline, false)
+    }
 }
-
 #[cfg(test)]
 mod test {
     use super::*;