refactor: move go-chi/binding into Gitea (#39528)

The `gitea.com/go-chi/binding` package only exists for Gitea, so it
moves into `modules/web/binding` to fix its bugs directly. Split out of
https://github.com/go-gitea/gitea/pull/39504.

- GET and HEAD always bind the query
- JSON `null` slice elements and nested `TrimSpace` fields bind
correctly
- Integer fields reject out-of-range values instead of wrapping
- An empty JSON body binds nothing and an unknown binding rule is an
error

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: bircni <bircni@icloud.com>

services/forms/admin.go

@@ -65,6 +65,6 @@ type AdminEditUserForm struct {
 // AdminDashboardForm form for admin dashboard operations
 type AdminDashboardForm struct {
 	middleware.FormDefaultValidator
-	Op   string `binding:"required"`
+	Op   string `binding:"Required"`
 	From string
 }