Make h:outputFormat support outputting to a request scope variable defined by a new var attribute

See the OmniFaces o:outputFormat for examples and description:

[http://showcase.omnifaces.org/components/outputFormat](http://showcase.omnifaces.org/components/outputFormat)

I've used this feature for building formatted text to use on h:commandLink buttons, and also to automatically escape URL parameter values that end up being used in my template when referencing CSS files (path parameters). When the URL parameter values are used without o:outputFormat we're able to execute XSS attacks. It would be really great if this feature were part of the 2.3 spec.

Start by reviewing the linked OmniFaces o:outputFormat examples and description, then compare them with Jakarta Faces h:outputFormat and the relevant specification. Done means defining how a new var attribute stores formatted output in request scope, including the described escaping behavior, and documenting the resulting 2.3 feature.

Written by the indexing model from the issue text.