chore: QoL improvements to tests (#7917)

- Use mock helper functions, instead of home-brew solutions.
- Disable cron jobs that are not important to be run during integration tests and might even interfere.
- Avoid sleeping unnecessary, if there's some requirement then sleep or retry until that requirement is met.
- Avoid trying to deliver webhooks that will always result in a failure.

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/7917
Reviewed-by: Michael Kriese <michael.kriese@gmx.de>
Co-authored-by: Gusted <postmaster@gusted.xyz>
Co-committed-by: Gusted <postmaster@gusted.xyz>

services/repository/fork_test.go

@@ -11,6 +11,7 @@ import (
 	user_model "forgejo.org/models/user"
 	"forgejo.org/modules/git"
 	"forgejo.org/modules/setting"
+	"forgejo.org/modules/test"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -36,7 +37,7 @@ func TestForkRepository(t *testing.T) {
 	assert.False(t, repo_model.IsErrReachLimitOfRepo(err))
 
 	// change AllowForkWithoutMaximumLimit to false for the test
-	setting.Repository.AllowForkWithoutMaximumLimit = false
+	defer test.MockVariableValue(&setting.Repository.AllowForkWithoutMaximumLimit, false)()
 	// user has reached maximum limit of repositories
 	user.MaxRepoCreation = 0
 	fork2, err := ForkRepositoryAndUpdates(git.DefaultContext, user, user, ForkRepoOptions{