Gin For RouteInfo struct, add a list of handlers instead of the last for middleware usage

Description

Hello everyone! Really like the library. However I have something which could help my OpenAPI generation library and I was hoping that this could help allow the library to work really well with middlewares. (The library is here if you're interested astra)

I would appreciate the ability to have the handler functions for the RouteInfo to have the entire chain of handler functions available, instead of the last - or at least maybe in another property.

// RouteInfo represents a request route's specification which contains method and path and its handler.
type RouteInfo struct {
    Method      string
    Path        string
    Handler     string
    HandlerFunc HandlerFunc
}

What I'd want to see if possible:

// RouteInfo represents a request route's specification which contains method and path and its handler.
type RouteInfo struct {
    Method      string
    Path        string
    Handler     string
    HandlerFunc HandlerFunc
        HandlersChain HandlersChain
}

Or I wouldn't be opposed to exposing the trees property of the Engine.

Let me know what you think! I'm happy to make this a reality if people would appreciate it and it wasn't a security concern.