Allow forward scheme for spring cloud gateway mvc similar to its webflux counterpart for declarative configuration using application properties or yaml

[mrinmoykhamrui]

Is your feature request related to a problem? Please describe.
webflux gateway allows forwarding using dispatcher handler (ForwardRoutingFilter) declaratively using application properties and yaml. Similar capability seems not available in mvc version of it.

Describe the solution you'd like
Ability to use forward scheme to configure gateway routes in application properties or yaml files. Any before filters applied on the request should be visible in the forwarded target

Describe alternatives you've considered
HandlerFunctions.forward is available for DSL based configuration however it seems any before filters applied on the request is not visible to the forward target.

[spencergibb]

See HandlerFunctions.forward(). It should be available to configuration. Are you seeing otherwise?

[spencergibb]

Caused by: java.lang.IllegalStateException: Unable to find HandlerFunction for scheme: forward
	at org.springframework.cloud.gateway.server.mvc.config.GatewayMvcPropertiesBeanDefinitionRegistrar.getRouterFunction(GatewayMvcPropertiesBeanDefinitionRegistrar.java:197) ~[classes/:na]
	at org.springframework.cloud.gateway.server.mvc.config.GatewayMvcPropertiesBeanDefinitionRegistrar.lambda$routerFunctionHolderSupplier$1(GatewayMvcPropertiesBeanDefinitionRegistrar.java:145) ~[classes/:na]
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1511) ~[na:na]
	at org.springframework.cloud.gateway.server.mvc.config.GatewayMvcPropertiesBeanDefinitionRegistrar.routerFunctionHolderSupplier(GatewayMvcPropertiesBeanDefinitionRegistrar.java:144) ~[classes/:na]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.obtainInstanceFromSupplier(AbstractAutowireCapableBeanFactory.java:1257) ~[spring-beans-6.1.4.jar:6.1.4]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.obtainInstanceFromSupplier(DefaultListableBeanFactory.java:951) ~[spring-beans-6.1.4.jar:6.1.4]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.obtainFromSupplier(AbstractAutowireCapableBeanFactory.java:1217) ~[spring-beans-6.1.4.jar:6.1.4]
	... 120 common frames omitted