feat: add optional timer schedule for container build

[matt-FFFFFF]

This pull request introduces support for automated, scheduled container registry image builds using Azure Container Registry (ACR) tasks. The main changes add configuration options for enabling and customizing the timer trigger schedule, and wire these options through all relevant modules for both Azure DevOps and GitHub scenarios. This ensures agent images are kept up-to-date with the latest patches and dependencies automatically.

Container Registry Task Timer Trigger Support:

• Added new variables container_registry_task_timer_trigger_enabled and container_registry_task_timer_trigger_schedule to modules/azure/variables.tf, alz/azuredevops/variables.tf, and alz/github/variables.tf for enabling and customizing the ACR task timer trigger. [1] [2] [3]
• Updated azurerm_container_registry_task resource in modules/azure/container_registry.tf to use the timer trigger, scheduling agent image builds according to the provided CRON expression and enablement flag.

Module Wiring and Variable Propagation:

• Passed the new timer trigger configuration variables through the azure module blocks in both alz/azuredevops/main.tf and alz/github/main.tf, ensuring they are available for downstream use. [1] [2]

General Refactoring for Consistency:

• Reordered and grouped module input variables in main.tf files for better readability and maintainability, with no functional changes. [1] [2]

Minor Formatting:

• Added a trailing newline in alz/azuredevops/main.tf for formatting consistency.