arrow2-convert migration 2: non-serde blueprint types (#3855)

This PR introduces `ObjectKind::Blueprint` into our codegen framework.

`Blueprint` objects are as expressive as `Datatype` objects (i.e. they
don't have the artificial limitations that we impose on `Component`
objects), but still implement the `Component` trait.
Blueprint objects live in a separate module so as not to pollute
LSP/docs/etc.

This allows us to replace existing `arrow2_convert`-based blueprint
types with fbs definitions instead.

This PR does not cover `SerdeField` shenanigans, that comes next.

crates/re_arrow_store/Cargo.toml

@@ -123,11 +123,6 @@ name = "arrow2"
 harness = false
 required-features = ["testing"]
 
-[[bench]]
-name = "arrow2_convert"
-harness = false
-required-features = ["testing"]
-
 [[bench]]
 name = "vectors"
 harness = false

crates/re_types/definitions/rerun/archetypes.fbs

@@ -24,4 +24,8 @@ include "./archetypes/view_coordinates.fbs";
 
 include "./testing/archetypes/fuzzy.fbs";
 
+// NOTE: The current file is the entrypoint for codegen, and so we need to import
+// the blueprint types here otherwise nothing will.
+include "./blueprint.fbs";
+
 namespace rerun.archetypes;

crates/re_types/definitions/rerun/blueprint.fbs

@@ -0,0 +1,2 @@
+include "./blueprint/auto_space_views.fbs";
+include "./blueprint/panel_view.fbs";

crates/re_types/definitions/rerun/blueprint/auto_space_views.fbs

@@ -0,0 +1,22 @@
+include "arrow/attributes.fbs";
+include "python/attributes.fbs";
+include "rust/attributes.fbs";
+
+include "rerun/datatypes.fbs";
+include "rerun/attributes.fbs";
+
+namespace rerun.blueprint;
+
+// ---
+
+/// A flag indicating space views should be automatically populated.
+///
+/// Unstable. Used for the ongoing blueprint experimentations.
+struct AutoSpaceViews (
+  "attr.arrow.transparent",
+  "attr.rust.derive": "Copy, Default",
+  "attr.rust.repr": "transparent",
+  "attr.rust.tuple_struct"
+) {
+  enabled: bool (order: 100);
+}

crates/re_types/definitions/rerun/blueprint/panel_view.fbs

@@ -0,0 +1,19 @@
+include "arrow/attributes.fbs";
+include "python/attributes.fbs";
+include "rust/attributes.fbs";
+
+include "rerun/datatypes.fbs";
+include "rerun/attributes.fbs";
+
+namespace rerun.blueprint;
+
+// ---
+
+/// The state of the panels.
+///
+/// Unstable. Used for the ongoing blueprint experimentations.
+struct PanelView (
+  "attr.rust.derive": "Copy"
+) {
+  is_expanded: bool (order: 100);
+}