SAML 2.0 filters should be in the web package

[jzheaux]

Saml2WebSsoAuthenticationFilter and Saml2WebSsoAuthenticationRequestFilter are in a package called .servlet.filter.

However, most other filters in Spring Security are in the .web package. Authentication filters specifically are in .web.authentication.

Saml2WebSsoAuthenticationFilter ought to be moved to .web.authentication
Saml2WebSsoAuthenticationRequestFilter ought to be moved to .web

Care should be taken to remain backward compatible which means deprecating the old classes. Also, the old classes would ideally delegate to the classes that are now in the correct location.