Reworked MS Teams deprecation warnings and notifications visibility

[Godmartinz]

This adds some grammatical corrections to deprecation warnings as well as:

• Fixes a bug when the webhook settings are cleared the deprecation message would persist.
• Separates deprecation notifications on the nav bar from inventory notifications, as well as making deprecation notifications only visible to those with super admin privileges.

#16127

[what-the-diff]

PR Summary

• Deprecation Date Extended for Microsoft Teams Webhook
  The original date of deprecation for Microsoft Teams webhook has been moved from January 31st, 2025, to December 31st, 2025, ensuring more time for users to adjust. Additionally, the deprecation check mechanism has been improved to consider whether a webhook had been selected.

• Enhanced Default Values Handling for Webhook Properties
  If the webhook isn't set, a new mechanism has been introduced into SlackSettingsForm.php to provide default values for various webhook properties, improving the general robustness of the application.

• Updated Deprecation Warning Message
  The warning message concerning the deprecation for Microsoft Teams, found within SlackSettingsForm.php, has been updated to reflect the newly amended deprecation date, ensuring clear and up-to-date communication to the users.

• Optimized Fetching of Alert Items
  The process to fetch alert items in default.blade.php has been updated. This change ensures that alerts are only queried when the flag to show them is active, resulting in more efficient usage of system resources.

• Streamlined Menu Rendering for Alerts
  The system for rendering the alert menu in default.blade.php has been simplified, resulting in cleaner code while maintaining the same level of access control for the system administrators.

[snipe]

The notification Icon will not show if there are no system notifications or inventory notifications.

I don't think that's the expected behavior. The icon should still show, it just won't have any badge next to it indicating number of notifications.

[snipe]

ping @Godmartinz

[snipe]

Still waiting on a of these changes I think?

[Godmartinz]

fixing conflicts