Clean up keyword lines in help (#7243)

# Description

This makes the help messages cleaner for keyword-style arguments.

Before:
```
  (optional) else_expression <Keyword([101, 108, 115, 101], Expression)>: expression or block to run if check fails
```

Now:
```
  (optional) "else" + <expression>: expression or block to run if check fails
```


# User-Facing Changes

Changes how help is printed, so we use slightly different shape names

# Tests + Formatting

Don't forget to add tests that cover your changes.

Make sure you've run and fixed any issues with these commands:

- `cargo fmt --all -- --check` to check standard code formatting (`cargo
fmt --all` applies these changes)
- `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used -A
clippy::needless_collect` to check that you're using the standard code
style
- `cargo test --workspace` to check that all tests pass

# After Submitting

If your PR had any user-facing changes, update [the
documentation](https://github.com/nushell/nushell.github.io) after the
PR is merged, if necessary. This will help us keep the docs up to date.

crates/nu-protocol/src/syntax_shape.rs

@@ -165,7 +165,15 @@ impl Display for SyntaxShape {
             SyntaxShape::GlobPattern => write!(f, "glob"),
             SyntaxShape::ImportPattern => write!(f, "import"),
             SyntaxShape::Block => write!(f, "block"),
-            SyntaxShape::Closure(_) => write!(f, "closure"),
+            SyntaxShape::Closure(args) => {
+                if let Some(args) = args {
+                    let arg_vec: Vec<_> = args.iter().map(|x| x.to_string()).collect();
+                    let arg_string = arg_vec.join(", ");
+                    write!(f, "closure({})", arg_string)
+                } else {
+                    write!(f, "closure()")
+                }
+            }
             SyntaxShape::Binary => write!(f, "binary"),
             SyntaxShape::Table => write!(f, "table"),
             SyntaxShape::List(x) => write!(f, "list<{}>", x),