Make tagged columnar updates work with mono-components too (#8769)

* Generate plural methods even for mono-components, so they can be used
with `send_columns`.
* Update `scalar_send_columns` snippet to use new columnar APIs.

```rust
const STEPS: i64 = 64;

let times = TimeColumn::new_sequence("step", 0..STEPS);
let scalars = (0..STEPS).map(|step| (step as f64 / 10.0).sin());

rec.send_columns_v2(
    "scalars",
    [times],
    rerun::Scalar::update_fields()
        .with_many_scalar(scalars)
        .columns(std::iter::repeat(1).take(STEPS as _))?
        .filter(|column| !column.descriptor.component_name.contains("Indicator")),
)?;
```

* Follow-up to #8753

crates/build/re_types_builder/src/codegen/rust/api.rs

@@ -1876,13 +1876,35 @@ fn quote_builder_from_obj(reporter: &Reporter, objects: &Objects, obj: &Object)
                 }
             }
         } else {
+            let quoted_many = obj.scope().is_none().then(|| {
+                let method_name_many = format_ident!("with_many_{field_name}");
+                let docstring_many = unindent::unindent(&format!("\
+                This method makes it possible to pack multiple [`{typ}`] in a single component batch.
+
+                This only makes sense when used in conjunction with [`Self::columns`]. [`Self::{method_name}`] should
+                be used when logging a single row's worth of data.
+                "));
+                let docstring_many = quote_doc_lines(&docstring_many.lines().map(|l| l.to_owned()).collect_vec());
+
+                quote !{
+                    #docstring_many
+                    #[inline]
+                    pub fn #method_name_many(mut self, #field_name: impl IntoIterator<Item = impl Into<#typ>>) -> Self {
+                        self.#field_name = try_serialize_field(Self::#descr_fn_name(), #field_name);
+                        self
+                    }
+                }
+            });
+
             quote! {
                 #docstring
                 #[inline]
                 pub fn #method_name(mut self, #field_name: impl Into<#typ>) -> Self {
                     self.#field_name = try_serialize_field(Self::#descr_fn_name(), [#field_name]);
                     self
                 }
+
+                #quoted_many
             }
         }
     });