C++ basic Archetype & Component logging (#2874)

* Part of #2647
* Next step after #2820

### What

Introduces APIs for component and archetype logging as well as the
necessary methods in codegen to do so. A very basic example is included
in `main.cpp`.
Largely unrelated to the rest:
* Makes C++ tagged union types copy-able
* `to_arrow_datatype` constructs/allocates the datatype lazily exactly
once (using C++'s crazy local `static` variable guarantees)

Commit by commit review possible.


![image](https://github.com/rerun-io/rerun/assets/1220815/8e7fdf3a-4fe7-45b1-a835-463b13fc34d8)

Next steps:
* Add roundtrip tests
* Add C++ to ci (roundtrip, linting, etc.)
* Add codegen custom code injection
* Improve API usability in varous places, including #2873 
* add other tests
* serialize unions
* serialize datatypes nested in unions, structs and lists
* more testing & roundtripping

### Checklist
* [x] I have read and agree to [Contributor
Guide](https://github.com/rerun-io/rerun/blob/main/CONTRIBUTING.md) and
the [Code of
Conduct](https://github.com/rerun-io/rerun/blob/main/CODE_OF_CONDUCT.md)
* [x] I've included a screenshot or gif (if applicable)
* [x] I have tested [demo.rerun.io](https://demo.rerun.io/pr/2874) (if
applicable)

- [PR Build Summary](https://build.rerun.io/pr/2874)
- [Docs
preview](https://rerun.io/preview/pr%3Aandreas%2Fcpp-codegen%2Farchetype-builder-and-logging/docs)
- [Examples
preview](https://rerun.io/preview/pr%3Aandreas%2Fcpp-codegen%2Farchetype-builder-and-logging/examples)

examples/cpp/minimal/main.cpp

@@ -1,29 +1,9 @@
 #include <loguru.hpp>
 #include <rerun.hpp>
 
+#include <array>
 #include <components/point2d.hpp>
 
-arrow::Result<std::shared_ptr<arrow::Table>> points2(size_t num_points, const float* xy) {
-    arrow::MemoryPool* pool = arrow::default_memory_pool();
-
-    ARROW_ASSIGN_OR_RAISE(auto builder, rr::components::Point2D::new_arrow_array_builder(pool));
-    ARROW_RETURN_NOT_OK(rr::components::Point2D::fill_arrow_array_builder(
-        builder.get(),
-        (const rr::components::Point2D*)
-            xy, // TODO(andreas): Hack to get Points2D C-style array in an easy fashion
-        num_points
-    ));
-
-    std::shared_ptr<arrow::Array> array;
-    ARROW_RETURN_NOT_OK(builder->Finish(&array));
-
-    auto name = "points"; // Unused, but should be the name of the field in the archetype
-    auto schema =
-        arrow::schema({arrow::field(name, rr::components::Point2D::to_arrow_datatype(), false)});
-
-    return arrow::Table::Make(schema, {array});
-}
-
 int main(int argc, char** argv) {
     loguru::g_preamble_uptime = false;
     loguru::g_preamble_thread = false;
@@ -33,37 +13,39 @@ int main(int argc, char** argv) {
 
     auto rr_stream = rr::RecordingStream{"c-example-app", "127.0.0.1:9876"};
 
-    // Points3D.
-    {
-        float xyz[9] = {0.0, 0.0, 0.0, 1.0, 2.0, 3.0, 5.0, 5.0, 5.0};
-        auto points = rr::points3(3, xyz).ValueOrDie(); // TODO(andreas): phase this out.
-        auto buffer = rr::ipc_from_table(*points).ValueOrDie();
-
-        const rr::DataCell data_cells[1] = {rr::DataCell{
-            .component_name = "rerun.point3d",
-            .num_bytes = static_cast<size_t>(buffer->size()),
-            .bytes = buffer->data(),
-        }};
-
-        uint32_t num_instances = 3;
-        rr_stream.log_data_row("3d/points", num_instances, 1, data_cells);
-    }
-
-    // Points2D.
-    {
-        float xy[6] = {0.0, 0.0, 1.0, 3.0, 5.0, 5.0};
-        auto points = points2(3, xy).ValueOrDie();
-        auto buffer = rr::ipc_from_table(*points).ValueOrDie();
-
-        const rr::DataCell data_cells[1] = {rr::DataCell{
-            .component_name = "rerun.point2d",
-            .num_bytes = static_cast<size_t>(buffer->size()),
-            .bytes = buffer->data(),
-        }};
-
-        uint32_t num_instances = 3;
-        rr_stream.log_data_row("2d/points", num_instances, 1, data_cells);
-    }
+    rr_stream.log_archetype(
+        "3d/points",
+        rr::archetypes::Points3D({
+                                     rr::datatypes::Point3D{1.0, 2.0, 3.0},
+                                     rr::datatypes::Point3D{4.0, 5.0, 6.0},
+                                 })
+            .with_radii({0.42, 0.43})
+            .with_colors({0xAA0000CC, 0x00BB00DD})
+            .with_labels({std::string("hello"), std::string("friend")})
+            .with_class_ids({126, 127})
+            .with_keypoint_ids({2, 3})
+            .with_instance_keys({66, 666})
+    );
+
+    rr::components::Label c_style_array[3] = {
+        rr::components::Label("hello"),
+        rr::components::Label("friend"),
+        rr::components::Label("yo"),
+    };
+    rr_stream.log_components(
+        "2d/points",
+        std::vector{
+            rr::components::Point2D(rr::datatypes::Point2D{0.0, 0.0}),
+            rr::components::Point2D(rr::datatypes::Point2D{1.0, 3.0}),
+            rr::components::Point2D(rr::datatypes::Point2D{5.0, 5.0}),
+        },
+        std::array{
+            rr::components::Color(0xFF0000FF),
+            rr::components::Color(0x00FF00FF),
+            rr::components::Color(0x0000FFFF),
+        },
+        c_style_array
+    );
 
     // Test some type instantiation
     auto tls = rr::datatypes::TranslationRotationScale3D{};