Add config_distro status to the Drupal status report page.

Problem/Motivation

When managing a Drupal site, administrators/devop/QA needs to stay informed about pending updates to modules and themes, as well as pending configuration updates. Currently, Drupal's status report page lacks a status message that includes the currently configured update mode (from config_distro), or if there are pending configuration updates. This omission can make it challenging for administrators to quickly identify and address pending configuration updates without going to the config distro ui or using drush.

Steps to reproduce

1. Visit the status report page of a Drupal site.
2. Note the absence of a status message indicating the currently configured update mode and any pending updates or configurations.

Proposed resolution

• Introduce a new status message to the status report page that appears if there are pending configuration updates that need to be applied.
• Ensure the status message is consistent with how Drupal handles pending database updates, indicating the urgency of resolving the issues.
• Include information about the number of pending updates, configurations, or database updates, as well as the currently configured update mode (e.g., manual or automatic).
• Optionally, provide a brief summary of what type of updates are pending (e.g., module updates, theme updates, Drupal core updates).
• Implement caching mechanisms to mitigate potential performance concerns, ensuring the status message is updated when necessary.
• Include both the currently set Update mode, and a link to config distro administration page.

Remaining tasks

• Implement the status message functionality.
• Test the status message under various scenarios to ensure it appears correctly and provides accurate information.
• Review and refine the caching mechanisms to optimize performance.
• Document the changes and update relevant documentation as necessary.

User interface changes

A new status message will be added to the status report page to indicate pending configuration updates.

API changes

None.

Data model changes

None.