feat: Gen3 blueprint geometry construction (#3869)

This PR implements building a tracking geometry using
the blueprint building mechanism.

```
           +---------------+  +-----------+
           |               |  |           |
           |     Root      |  |           v
           |               |  |   +---------------+
           +---------------+  |   |               |
                   |          |   |    Child 1    |
        +----------+          |   |               |
        v          +----------+   +---------------+
+---------------+                         |
|               |          +--------------+
|    Child 2    |          v         +----------+
|               |     .---------.    |          |
+---------------+    /           \   |          v
                    (  Proc node  )  |  +---------------+
                     `.         ,'   |  |               |
                       `-------'     |  |    Child 3    |
                           |         |  |               |
                           |         |  +---------------+
                           +---------+
```

The construction phases are documented in @c BlueprintNode, which is the
base class for all nodes in the tree.


Part of:
- #3502 

Blocked by:
- #3816 
- #3818
- #3971

Core/include/Acts/Geometry/Blueprint.hpp

@@ -0,0 +1,105 @@
+// This file is part of the ACTS project.
+//
+// Copyright (C) 2016 CERN for the benefit of the ACTS project
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#pragma once
+
+#include "Acts/Geometry/BlueprintNode.hpp"
+#include "Acts/Geometry/PortalShell.hpp"
+#include "Acts/Geometry/TrackingGeometry.hpp"
+#include "Acts/Geometry/TrackingVolume.hpp"
+
+namespace Acts {
+
+class GeometryContext;
+
+/// This class is the top-level entry point to build a tracking geometry using
+/// the blueprint building mechanism. It forms the root of a tree of nodes where
+/// each node performs a portion of the construction. This top-level class has
+/// the main construction methods that execute the construction of the geometry.
+///
+/// ```
+///            +---------------+  +-----------+
+///            |               |  |           |
+///            |     Root      |  |           v
+///            |               |  |   +---------------+
+///            +---------------+  |   |               |
+///                    |          |   |    Child 1    |
+///         +----------+          |   |               |
+///         v          +----------+   +---------------+
+/// +---------------+                         |
+/// |               |          +--------------+
+/// |    Child 2    |          v         +----------+
+/// |               |     .---------.    |          |
+/// +---------------+    /           \   |          v
+///                     (  Proc node  )  |  +---------------+
+///                      `.         ,'   |  |               |
+///                        `-------'     |  |    Child 3    |
+///                            |         |  |               |
+///                            |         |  +---------------+
+///                            +---------+
+/// ```
+///
+/// The construction phases are documented in @c BlueprintNode, which is the
+/// base class for all nodes in the tree.
+/// @note This class inherits from @c BlueprintNode, but hides the main
+///       blueprint construction phase overloads. The @c Blueprint class is
+///       only ever intended to be the top-level node, and not anywhere else
+///       in the tree.
+class Blueprint : public BlueprintNode {
+ public:
+  struct Config {
+    /// Determine how much envelope space to produce from the highest volume
+    /// in the geometry hierarchy and the world volume.
+    ExtentEnvelope envelope = ExtentEnvelope::Zero();
+
+    /// The geometry identifier hook, passed through the `TrackingGeometry`
+    /// constructor. This will be superseded by a more integrated approach to
+    /// the identification scheme
+    GeometryIdentifierHook geometryIdentifierHook = {};
+  };
+
+  /// Constructor from a config object
+  /// @param config The configuration object
+  explicit Blueprint(const Config& config);
+
+  /// Construct the tracking geometry from the blueprint tree
+  /// @param options The construction options, see @c BlueprintOptions
+  /// @param gctx The geometry context for construction. In almost all cases,
+  ///             this should be the *nominal* geometry context
+  /// @param logger The logger to use for output during construction
+  std::unique_ptr<TrackingGeometry> construct(
+      const BlueprintOptions& options, const GeometryContext& gctx,
+      const Logger& logger = Acts::getDummyLogger());
+
+ protected:
+  /// The name of the blueprint node, always "Root"
+  /// @return The name
+  const std::string& name() const override;
+
+  /// @copydoc BlueprintNode::build
+  Volume& build(const BlueprintOptions& options, const GeometryContext& gctx,
+                const Logger& logger = Acts::getDummyLogger()) override;
+
+  /// @copydoc BlueprintNode::connect
+  PortalShellBase& connect(
+      const BlueprintOptions& options, const GeometryContext& gctx,
+      const Logger& logger = Acts::getDummyLogger()) override;
+
+  /// @copydoc BlueprintNode::finalize
+  void finalize(const BlueprintOptions& options, const GeometryContext& gctx,
+                TrackingVolume& parent,
+                const Logger& logger = Acts::getDummyLogger()) override;
+
+  /// @copydoc BlueprintNode::addToGraphviz
+  void addToGraphviz(std::ostream& os) const override;
+
+ private:
+  Config m_cfg;
+};
+
+}  // namespace Acts