dra: add "named resources" structured parameter model

Like the current device plugin interface, a DRA driver using this model
announces a list of resource instances. In contrast to device plugins, this
list is made available to the scheduler together with attributes that can be
used to select suitable instances when they are not all alike.

Because this is the first structured parameter model, some checks that
previously were not possible, in particular "is one structured parameter field
set", now gets enabled. Adding another structured parameter model will be
similar.

The applyconfigs code generator assumes that all types in an API are defined in
a single package. If it wasn't for that, it would be possible to place the
"named resources" types in separate packages, which makes their names in the Go
code more natural and provides an indication of their stability level because
the package name could include a version.

pkg/scheduler/framework/plugins/dynamicresources/structured/namedresources/namedresourcesmodel.go

@@ -0,0 +1,150 @@
+/*
+Copyright 2024 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package namedresources
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"slices"
+
+	resourceapi "k8s.io/api/resource/v1alpha2"
+	"k8s.io/apiserver/pkg/cel/environment"
+	"k8s.io/dynamic-resource-allocation/structured/namedresources/cel"
+)
+
+type Model struct {
+	instances []instanceAllocation
+}
+
+type instanceAllocation struct {
+	allocated bool
+	instance  *resourceapi.NamedResourcesInstance
+}
+
+// AddResources must be called first to create entries for all existing
+// resource instances. The resources parameter may be nil.
+func AddResources(m *Model, resources *resourceapi.NamedResourcesResources) {
+	if resources == nil {
+		return
+	}
+
+	for i := range resources.Instances {
+		m.instances = append(m.instances, instanceAllocation{instance: &resources.Instances[i]})
+	}
+}
+
+// AddAllocation may get called after AddResources to mark some resource
+// instances as allocated. The result parameter may be nil.
+func AddAllocation(m *Model, result *resourceapi.NamedResourcesAllocationResult) {
+	if result == nil {
+		return
+	}
+	for i := range m.instances {
+		if m.instances[i].instance.Name == result.Name {
+			m.instances[i].allocated = true
+			break
+		}
+	}
+}
+
+func NewClaimController(filter *resourceapi.NamedResourcesFilter, requests []*resourceapi.NamedResourcesRequest) (*Controller, error) {
+	c := &Controller{}
+	if filter != nil {
+		compilation := cel.Compiler.CompileCELExpression(filter.Selector, environment.StoredExpressions)
+		if compilation.Error != nil {
+			// Shouldn't happen because of validation.
+			return nil, fmt.Errorf("compile class filter CEL expression: %w", compilation.Error)
+		}
+		c.filter = &compilation
+	}
+	for _, request := range requests {
+		compilation := cel.Compiler.CompileCELExpression(request.Selector, environment.StoredExpressions)
+		if compilation.Error != nil {
+			// Shouldn't happen because of validation.
+			return nil, fmt.Errorf("compile request CEL expression: %w", compilation.Error)
+		}
+		c.requests = append(c.requests, compilation)
+	}
+	return c, nil
+}
+
+type Controller struct {
+	filter   *cel.CompilationResult
+	requests []cel.CompilationResult
+}
+
+func (c *Controller) NodeIsSuitable(ctx context.Context, model Model) (bool, error) {
+	indices, err := c.allocate(ctx, model)
+	return len(indices) == len(c.requests), err
+}
+
+func (c *Controller) Allocate(ctx context.Context, model Model) ([]*resourceapi.NamedResourcesAllocationResult, error) {
+	indices, err := c.allocate(ctx, model)
+	if err != nil {
+		return nil, err
+	}
+	if len(indices) != len(c.requests) {
+		return nil, errors.New("insufficient resources")
+	}
+	results := make([]*resourceapi.NamedResourcesAllocationResult, len(c.requests))
+	for i := range c.requests {
+		results[i] = &resourceapi.NamedResourcesAllocationResult{Name: model.instances[indices[i]].instance.Name}
+	}
+	return results, nil
+}
+
+func (c *Controller) allocate(ctx context.Context, model Model) ([]int, error) {
+	// Shallow copy, we need to modify the allocated boolean.
+	instances := slices.Clone(model.instances)
+	indices := make([]int, 0, len(c.requests))
+
+	for _, request := range c.requests {
+		for i, instance := range instances {
+			if instance.allocated {
+				continue
+			}
+			if c.filter != nil {
+				okay, err := c.filter.Evaluate(ctx, instance.instance.Attributes)
+				if err != nil {
+					return nil, fmt.Errorf("evaluate filter CEL expression: %w", err)
+				}
+				if !okay {
+					continue
+				}
+			}
+			okay, err := request.Evaluate(ctx, instance.instance.Attributes)
+			if err != nil {
+				return nil, fmt.Errorf("evaluate request CEL expression: %w", err)
+			}
+			if !okay {
+				continue
+			}
+			// Found a matching, unallocated instance. Let's use it.
+			//
+			// A more thorough search would include backtracking because
+			// allocating one "large" instances for a "small" request may
+			// make a following "large" request impossible to satisfy when
+			// only "small" instances are left.
+			instances[i].allocated = true
+			indices = append(indices, i)
+			break
+		}
+	}
+	return indices, nil
+
+}