Explain with more detail the alerts behavior - 4.9 changes

[pereyra-m]

Description

These are the same changes of #7861 but for v4.9.

This PR updates the description of the vulnerability scanner module so the issue can understand when to expect an alert and when not.
I've also made a reference to the PoC to show an example of the vulnerabilities inventory.

The alert generation schema was also updated.

Checks

Docs building

• Compiles without warnings.

Writing style

• Uses present tense, active voice, and semi-formal registry.
• Uses short, simple sentences.