Alerting: add support for name and description properties in Notification Policies

**Why is this needed**: The notification policy tree offers a convenient structure to manage large-scale alerting setups. A node can define a specific scope for a team: - Broader scope levels can catch broad alerts to ensure alerts in this scope are not missed. - Lower levels can refine specific cases like critical alerts or particular services. - New branches can be added without affecting existing policies. While admins are familiar with the tree's structure and intent, individual team members (e.g., viewer roles ) may find it challenging to navigate the tree or understand the purpose of each policy or their assigned branch. Recently, we received the following feedback: > If Team A wants to set up an alert independently, they must fully understand how the notification policy works. The easiest solution is to use the contact point selector, which is more straightforward. While routing through labels is a powerful feature, it is inherently more complex than selecting a contact point. This feedback highlights a significant gap: notification policies lack the ability to convey their intent clearly. Notification policies currently display only label information, leaving little context for alert users. <img width="965" alt="Image" src="https://github.com/user-attachments/assets/a13b2b4b-39a4-4568-ad28-d3b9d2cae850" /> **What would you like to be added**: Introduce optional name and description fields for notification policies. These fields would allow administrators to annotate each policy with: - A name to identify the purpose of the policy at a glance. - A detailed description to explain which alerts the policy manages, its purpose, and how it handles their alerts. **Who is this feature for?** This addition facilitates collaboration between policy admins and alert users, and hopefully encourages the practice of using policies more intentionally.