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>

modules/structs/user.go

@@ -89,7 +89,7 @@ type UserSettings struct {
 // swagger:model
 type UserSettingsOptions struct {
 	FullName      *string `json:"full_name" binding:"MaxSize(100)"`
-	Website       *string `json:"website" binding:"OmitEmpty;ValidUrl;MaxSize(255)"`
+	Website       *string `json:"website" binding:"ValidUrl;MaxSize(255)"`
 	Description   *string `json:"description" binding:"MaxSize(255)"`
 	Location      *string `json:"location" binding:"MaxSize(50)"`
 	Language      *string `json:"language"`