Added Ubuntu 26.04 OS support

[SAYUK09]

Key Changes:

OS Configuration Files:

• Added complete package configuration for Ubuntu 26.04 (x86_64 and aarch64):
  • default_packages.json, additional_packages.json, admin_debug_packages.json
  • service_k8s_v1.35.1.json, slurm_custom.json, ucx.json
  • ldms.json, openldap.json, openmpi.json, csi_driver_powerscale.json

Pulp and Local Repo:

• Updated local_repo_config.yml with Ubuntu OS URLs (archive.ubuntu.com)
• Added Pulp deb plugin support in prepare_oim/roles/deploy_containers/pulp/vars/main.yml
• Updated metadata creation and RPM processing for deb packages

Image Builder:

• Added Ubuntu image build support with patched scripts:
  • image-builder-installer.py - Uses buildah run for apt operations, handles self-signed certs
  • image-builder-layer.py - Ubuntu-specific layer handling
  • image-builder-publish.py - Ubuntu publish support
• Added Ubuntu base/compute image build tasks and config templates
• Updated mount configurations for Ubuntu builds

Provisioning:

• Added OS-specific CA trust handling (update-ca-trust vs update-ca-certificates)
• Added OS-specific Slurm plugin directory paths
• Updated cloud-init templates for Ubuntu Slurm controller and compute nodes
• Updated BSS configuration for OS-agnostic image paths
• Fixed Slurmdbd StorageHost to use localhost
• Updated K8s config for Ubuntu CA certificate handling

Validation:

• Added OS type detection in various validation tasks

Testing:

• Verified Ubuntu 26.04 image builds with Wolfi-based image-builder
• Successfully PXE booted Slurm controller and one compute node