Refactor web route (#24080)

The old code is unnecessarily complex, and has many misuses.

Old code "wraps" a lot, wrap wrap wrap, it's difficult to understand
which kind of handler is used.

The new code uses a general approach, we do not need to write all kinds
of handlers into the "wrapper", do not need to wrap them again and
again.

New code, there are only 2 concepts:

1. HandlerProvider: `func (h any) (handlerProvider func (next)
http.Handler)`, it can be used as middleware
2. Use HandlerProvider to get the final HandlerFunc, and use it for
`r.Get()`


And we can decouple the route package from context package (see the
TODO).

# FAQ

## Is `reflect` safe?

Yes, all handlers are checked during startup, see the `preCheckHandler`
comment. If any handler is wrong, developers could know it in the first
time.

## Does `reflect` affect performance?

No. https://github.com/go-gitea/gitea/pull/24080#discussion_r1164825901

1. This reflect code only runs for each web handler call, handler is far
more slower: 10ms-50ms
2. The reflect is pretty fast (comparing to other code): 0.000265ms
3. XORM has more reflect operations already

routers/install/routes.go

@@ -81,14 +81,14 @@ func installRecovery(ctx goctx.Context) func(next http.Handler) http.Handler {
 	}
 }
 
-// Routes registers the install routes
+// Routes registers the installation routes
 func Routes(ctx goctx.Context) *web.Route {
 	r := web.NewRoute()
 	for _, middle := range common.Middlewares() {
 		r.Use(middle)
 	}
 
-	r.Use(web.WrapWithPrefix("/assets/", public.AssetsHandlerFunc("/assets/"), "AssetsHandler"))
+	r.Use(web.MiddlewareWithPrefix("/assets/", nil, public.AssetsHandlerFunc("/assets/")))
 
 	r.Use(session.Sessioner(session.Options{
 		Provider:       setting.SessionConfig.Provider,
@@ -109,7 +109,7 @@ func Routes(ctx goctx.Context) *web.Route {
 	r.Get("/post-install", InstallDone)
 	r.Get("/api/healthz", healthcheck.Check)
 
-	r.NotFound(web.Wrap(installNotFound))
+	r.NotFound(installNotFound)
 	return r
 }