build: update k8s names to use device-mgmt-toolkit

[rsdmike]

#401

[Copilot]

Pull Request Overview

This PR updates Kubernetes resource names and references to use "device-mgmt-toolkit" instead of "open-amt" naming convention, aligning with the new project branding.

• Replace "open-amt" prefixes with "device-mgmt-toolkit" across K8s secrets, plugins, and configurations
• Update Helm chart artifact naming from "open-amt-toolkit" to "device-mgmt-toolkit"
• Maintain functional consistency while standardizing naming convention

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
kubernetes/charts/templates/mps.yaml	Updates secret references to use device-mgmt-toolkit naming
kubernetes/charts/templates/kong.yaml	Renames Kong plugins and credentials from open-amt to device-mgmt naming
kubernetes/charts/secrets.yaml	Updates secret names and ACL groups to device-mgmt-toolkit convention
.github/workflows/helm-tgz-asset.yml	Changes Helm tarball artifact name and description to device-mgmt-toolkit

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