API changes for Pod Level Resources

1. Add Resources struct to PodSpec struct in both external and internal API packages
2. Adding feature gate and logic for dropping disabled fields for Pod Level Resources
KEP: enhancements/keps/sig-node/2837-pod-level-resource-spec

Kubernetes-commit: d7f488b5e341dec8f6ef180f488e788a4103821c

Author: ndixita

Diff for: core/v1/types.go

@@ -4087,6 +4087,20 @@ type PodSpec struct {
 	// +featureGate=DynamicResourceAllocation
 	// +optional
 	ResourceClaims []PodResourceClaim `json:"resourceClaims,omitempty" patchStrategy:"merge,retainKeys" patchMergeKey:"name" protobuf:"bytes,39,rep,name=resourceClaims"`
+	// Resources is the total amount of CPU and Memory resources required by all
+	// containers in the pod. It supports specifying Requests and Limits for
+	// "cpu" and "memory" resource names only. ResourceClaims are not supported.
+	//
+	// This field enables fine-grained control over resource allocation for the
+	// entire pod, allowing resource sharing among containers in a pod.
+	// TODO: For beta graduation, expand this comment with a detailed explanation.
+	//
+	// This is an alpha field and requires enabling the PodLevelResources feature
+	// gate.
+	//
+	// +featureGate=PodLevelResources
+	// +optional
+	Resources *ResourceRequirements `json:"resources,omitempty" protobuf:"bytes,40,opt,name=resources"`
 }
 
 // PodResourceClaim references exactly one ResourceClaim, either directly