This commit deprecates the `<mvc:*` XML configuration namespace for
configuring Spring MVC applications. This configuration model is lagging
behind in the 6.x generation already and we don't intend to invest in
this space to close that gap.
As of 7.0, using this XML namespace will result in a WARN log message.
This commit also states our intent in the reference documentation.
Closes gh-34063
4fd368b1af