The function bean can be declared as a `FactoryBean`,
for example with Spring Integration's `GatewayProxyFactoryBean`.
See `LogConsumerConfiguration` in Spring Functions Catalog project.
* Fix `FunctionTypeUtils` to react to the `ParameterizedType`
and check its assignments against `Factory` bean.
Then resolves its generic to the proper target function type.
* Add `BeanFactoryAwareFunctionRegistryTests.functionFromFactoryBeanIsProperlyResolved()`
to verify that `FactoryBean<Function<?, ?>>` is resolved properly
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