Split "modules/context.go" to separate files (#24569)

The "modules/context.go" is too large to maintain.

This PR splits it to separate files, eg: context_request.go,
context_response.go, context_serve.go

This PR will help:

1. The future refactoring for Gitea's web context (eg: simplify the context)
2. Introduce proper "range request" support
3. Introduce context function

This PR only moves code, doesn't change any logic.

routers/web/auth/auth.go

@@ -444,7 +444,7 @@ func SignUpPost(ctx *context.Context) {
 	}
 	if !password.IsComplexEnough(form.Password) {
 		ctx.Data["Err_Password"] = true
-		ctx.RenderWithErr(password.BuildComplexityError(ctx), tplSignUp, &form)
+		ctx.RenderWithErr(password.BuildComplexityError(ctx.Locale), tplSignUp, &form)
 		return
 	}
 	pwned, err := password.IsPwned(ctx, form.Password)