[VSA] Add Warning Banner about behavior change in calculation in 15.0

What does this MR do and why?

This MR adds an informational message to group-level VSA about a behavior change in data calculation that will be introduced in %15.0

Screenshots or screen recordings

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #343209 (closed)