Allow idiomatic usage of middlewares in gorilla/mux (#9802)

Historically due to lack of support for middlewares
we ended up writing wrapped handlers for all
middlewares on top of the gorilla/mux, this causes
multiple issues when we want to let's say

- Overload r.Body with some custom implementation
  to track the incoming Reads()
- Add other sort of top level checks to avoid
  DDOSing the server with large incoming HTTP
  bodies.

Since 1.7.x release gorilla/mux provides proper
use of middlewares, which are honored by the muxer
directly. This makes sure that Go can honor its
own internal ServeHTTP(w, r) implementation where
Go net/http can wrap into its own customer readers.

This PR as a side-affect fixes rare issues of client
hangs which were reported in the wild but never really
understood or fixed in our codebase.

Fixes #9759
Fixes #7266
Fixes #6540
Fixes #5455
Fixes #5150

Refer https://github.com/boto/botocore/pull/1328 for
one variation of the same issue in #9759

cmd/routers.go

@@ -38,7 +38,7 @@ func registerDistXLRouters(router *mux.Router, endpointZones EndpointZones) {
 }
 
 // List of some generic handlers which are applied for all incoming requests.
-var globalHandlers = []HandlerFunc{
+var globalHandlers = []MiddlewareFunc{
 	// set x-amz-request-id header.
 	addCustomHeaders,
 	// set HTTP security headers such as Content-Security-Policy.
@@ -118,6 +118,6 @@ func configureServerHandler(endpointZones EndpointZones) (http.Handler, error) {
 	router.NotFoundHandler = http.HandlerFunc(httpTraceAll(errorResponseHandler))
 	router.MethodNotAllowedHandler = http.HandlerFunc(httpTraceAll(errorResponseHandler))
 
-	// Register rest of the handlers.
-	return registerHandlers(router, globalHandlers...), nil
+	router.Use(registerMiddlewares)
+	return router, nil
 }