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>

services/repository/archiver/archiver_test.go

@@ -24,7 +24,7 @@ func TestMain(m *testing.M) {
 func TestArchive_Basic(t *testing.T) {
 	assert.NoError(t, unittest.PrepareTestDatabase())
 
-	ctx := test.MockContext(t, "user27/repo49")
+	ctx, _ := test.MockContext(t, "user27/repo49")
 	firstCommit, secondCommit := "51f84af23134", "aacbdfe9e1c4"
 
 	test.LoadRepo(t, ctx, 49)