show the full directory / file path in "directory not found" error (#10430)

should close https://github.com/nushell/nushell/issues/10406

# Description
when writing a script, with variables you try to `ls` or `open`, you
will get a "directory not found" error but the variable won't be
expanded and you won't be able to see which one of the variable was the
issue...

this PR adds this information to the error.

# User-Facing Changes
let's define a variable
```nushell
let does_not_exist = "i_do_not_exist_in_the_current_directory"
```
### before
```nushell
> open $does_not_exist
Error: nu:🐚:directory_not_found

  × Directory not found
   ╭─[entry #7:1:1]
 1 │ open $does_not_exist
   ·      ───────┬───────
   ·             ╰── directory not found
   ╰────
```
```nushell
> ls $does_not_exist
Error: nu:🐚:directory_not_found

  × Directory not found
   ╭─[entry #8:1:1]
 1 │ ls $does_not_exist
   ·    ───────┬───────
   ·           ╰── directory not found
   ╰────
```

### after
```nushell
> open $does_not_exist
Error: nu:🐚:directory_not_found

  × Directory not found
   ╭─[entry #3:1:1]
 1 │ open $does_not_exist
   ·      ───────┬───────
   ·             ╰── directory not found
   ╰────
  help: /home/amtoine/documents/repos/github.com/amtoine/nushell/i_do_not_exist_in_the_current_directory does not exist
```
```nushell
> ls $does_not_exist
Error: nu:🐚:directory_not_found

  × Directory not found
   ╭─[entry #4:1:1]
 1 │ ls $does_not_exist
   ·    ───────┬───────
   ·           ╰── directory not found
   ╰────
  help: /home/amtoine/documents/repos/github.com/amtoine/nushell/i_do_not_exist_in_the_current_directory does not exist
```

# Tests + Formatting
shouldn't harm anything 🤞 

# After Submitting

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

@@ -391,7 +391,7 @@ fn copy_to_non_existing_dir_impl(progress: bool) {
             progress_flag
         );
         assert!(actual.err.contains("directory not found"));
-        assert!(actual.err.contains("destination directory does not exist"));
+        assert!(actual.err.contains("does not exist"));
     });
 }