chore: move all test blank imports in a single package (#10662)

- Create `modules/testimport/import.go` to centralize blank import needed for tests (in order to run the `init` function)  to simplify maintenance.
- Remove the imports that are not needed.

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/10662
Reviewed-by: Michael Kriese <michael.kriese@gmx.de>
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Co-authored-by: limiting-factor <limiting-factor@posteo.com>
Co-committed-by: limiting-factor <limiting-factor@posteo.com>

services/issue/comments_test.go

@@ -18,8 +18,6 @@ import (
 	issue_service "forgejo.org/services/issue"
 	"forgejo.org/tests"
 
-	_ "forgejo.org/services/webhook"
-
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )

services/issue/main_test.go

@@ -9,8 +9,6 @@ import (
 	"forgejo.org/models/unittest"
 	"forgejo.org/modules/setting"
 	"forgejo.org/services/webhook"
-
-	_ "forgejo.org/models/actions"
 )
 
 func TestMain(m *testing.M) {