Support Multi-Select in Notification Source

Feature Add feature issue reference Currently, users need to create separate alerts when the only variation is the Notification Source (e.g., Dashboard vs. Table). This makes the process time-consuming, especially when conditions remain the same across multiple entity types.

Describe the task A clear and concise description of what the bug is.

• Allow multi-select for Notification Source when creating alerts.
• Ensure that only common filters between selected sources are available to avoid conflicts.
• Apply this change to entities implementing EntityInterface to maintain compatibility.