Refactor web package and context package (#25298)

1. The "web" package shouldn't depends on "modules/context" package,
instead, let each "web context" register themselves to the "web"
package.
2. The old Init/Free doesn't make sense, so simplify it
* The ctx in "Init(ctx)" is never used, and shouldn't be used that way
* The "Free" is never called and shouldn't be called because the SSPI
instance is shared

---------

Co-authored-by: Giteabot <teabot@gitea.io>

tests/integration/integration_test.go

@@ -87,7 +87,7 @@ func TestMain(m *testing.M) {
 	defer cancel()
 
 	tests.InitTest(true)
-	c = routers.NormalRoutes(context.TODO())
+	c = routers.NormalRoutes()
 
 	// integration test settings...
 	if setting.CfgProvider != nil {