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>

tests/integration/issue_test.go

@@ -123,7 +123,6 @@ func TestViewIssuesKeyword(t *testing.T) {
 		Index:  1,
 	})
 	issues.UpdateIssueIndexer(t.Context(), issue.ID)
-	time.Sleep(time.Second * 1)
 
 	const keyword = "first"
 	req := NewRequestf(t, "GET", "%s/issues?q=%s", repo.Link(), keyword)