Method jakarta.servlet.http.HttpSession#getAttribute should be generic typed

In Jakarta 11, the return type of the jakarta.servlet.http.HttpSession#getAttribute method is Object.

It would be better if the return type could be defined:
`var attribute = httpSession.getAttribute("attribute");`

The type signature would look like this:
` T getAttribute(String name)`

The issue targets the jakarta.servlet.http.HttpSession#getAttribute declaration; start by reading its current API definition and the Jakarta Servlet compatibility guidance. Determine whether the proposed generic signature is appropriate for Jakarta Servlet 11 and verify the decision against API compatibility requirements; done means the signature question is resolved.

Written by the indexing model from the issue text.