pkg/web: remove dependency injection (#49123)

* pkg/web: store http.Handler internally

* pkg/web: remove injection

Removes any injection code from pkg/web.

It already was no longer functional, as we already only injected into
`http.Handler`, meaning we only inject ctx.Req and ctx.Resp.

Any other types (*Context, *ReqContext) were already accessed using the
http.Request.Context.Value() method.

* *: remove type mappings

Removes any call to the previously removed TypeMapper, as those were
non-functional already.

* pkg/web: remove Context.Invoke

was no longer used outside of pkg/web and also no longer functional

pkg/web/router.go

@@ -146,13 +146,13 @@ func (r *Router) Handle(method string, pattern string, handlers []Handler) {
 		h = append(h, handlers...)
 		handlers = h
 	}
-	handlers = validateAndWrapHandlers(handlers)
+	httpHandlers := validateAndWrapHandlers(handlers)
 
 	r.handle(method, pattern, func(resp http.ResponseWriter, req *http.Request, params map[string]string) {
 		c := r.m.createContext(resp, SetURLParams(req, params))
-		c.handlers = make([]Handler, 0, len(r.m.handlers)+len(handlers))
+		c.handlers = make([]http.Handler, 0, len(r.m.handlers)+len(handlers))
 		c.handlers = append(c.handlers, r.m.handlers...)
-		c.handlers = append(c.handlers, handlers...)
+		c.handlers = append(c.handlers, httpHandlers...)
 		c.run()
 	})
 }
@@ -194,12 +194,12 @@ func (r *Router) Any(pattern string, h ...Handler) { r.Handle("*", pattern, h) }
 // found. If it is not set, http.NotFound is used.
 // Be sure to set 404 response code in your handler.
 func (r *Router) NotFound(handlers ...Handler) {
-	handlers = validateAndWrapHandlers(handlers)
+	httpHandlers := validateAndWrapHandlers(handlers)
 	r.notFound = func(rw http.ResponseWriter, req *http.Request) {
 		c := r.m.createContext(rw, req)
-		c.handlers = make([]Handler, 0, len(r.m.handlers)+len(handlers))
+		c.handlers = make([]http.Handler, 0, len(r.m.handlers)+len(handlers))
 		c.handlers = append(c.handlers, r.m.handlers...)
-		c.handlers = append(c.handlers, handlers...)
+		c.handlers = append(c.handlers, httpHandlers...)
 		c.run()
 	}
 }