DRA quota: add ResourceClaim v1.ResourceQuota limits

Dynamic resource allocation is similar to storage in the sense that users
create ResourceClaim objects to request resources, same as with persistent
volume claims. The actual resource usage is only known when allocating claims,
but some limits can already be enforced at admission time:

- "count/resourceclaims.resource.k8s.io" limits the number of ResourceClaim objects in
  a namespace; this is a generic feature that is already supported also without
  this commit.

- "resourceclaims" is *not* an alias - use "count/resourceclaims.resource.k8s.io"
  instead.

- <device-class-name>.deviceclass.resource.k8s.io/devices limits the number of
  ResourceClaim objects in a namespace such that the number of devices
  requested through those objects with that class does not exceed the limit.

A single request may cause the allocation of multiple devices. For exact
counts, the quota limit is based on the sum of those exact counts. For requests
asking for "all" matching devices, the maximum number of allocated devices per
claim is used as a worst-case upper bound.

Requests asking for "admin access" contribute to the quota.

DRA quota: remove admin mode exception

pkg/apis/core/types.go

@@ -5799,6 +5799,8 @@ const (
 	ResourceLimitsMemory ResourceName = "limits.memory"
 	// Local ephemeral storage limit, in bytes. (500Gi = 500GiB = 500 * 1024 * 1024 * 1024)
 	ResourceLimitsEphemeralStorage ResourceName = "limits.ephemeral-storage"
+	// resource.k8s.io devices requested with a certain DeviceClass, number
+	ResourceClaimsPerClass string = ".deviceclass.resource.k8s.io/devices"
 )
 
 // The following identify resource prefix for Kubernetes object types