[alerter]optimize: Append not resolved alert description to resolved alert

[loong95]

What's changed?

related issue

Enhanced the resolved alert description by appending the trigger alert's description, improving the context provided during alert resolution.

Suppose an alert is triggered with the following content:

The xxx server is in exception.

Before the modification, the resolved alert description was:

Alert Resolved Notice: status > 0

After the modification, the description becomes:

Alert Resolved Notice: The xxx server is in exception.

Checklist

• [x] I have read the Contributing Guide
• [x] I have written the necessary doc or comment.
• [x] I have added the necessary unit tests and all cases have passed.

Add or update API

• [x] I have added the necessary e2e tests and all cases have passed.