[TESTS] Move CreateDeclarativeRepo to more accessible location

- This allows `CreateDeclarativeRepo` to be used by other testing
packages such as E2EE testing.
- Removes unused function in `services/webhook/sourcehut/builds_test.go`.

tests/integration/mirror_push_test.go

@@ -167,7 +167,7 @@ func TestSSHPushMirror(t *testing.T) {
 		srcRepo := unittest.AssertExistsAndLoadBean(t, &repo_model.Repository{ID: 2})
 		assert.False(t, srcRepo.HasWiki())
 		sess := loginUser(t, user.Name)
-		pushToRepo, _, f := CreateDeclarativeRepoWithOptions(t, user, DeclarativeRepoOptions{
+		pushToRepo, _, f := tests.CreateDeclarativeRepoWithOptions(t, user, tests.DeclarativeRepoOptions{
 			Name:         optional.Some("push-mirror-test"),
 			AutoInit:     optional.Some(false),
 			EnabledUnits: optional.Some([]unit.Type{unit.TypeCode}),