Improve UX for scheduling builds for newly pushed branches on the CI

Currently, builds have to be scheduled manually, once the jobs appear on Jenkins. The cronjob to update the jobs runs every 5 min, and the jobs update takes 1-2 min. The resulting worflow is:

1. Push branch with changes you want to test
2. Wait 2-7 minutes until the corresponding job appears on Jenkins
3. Manually schedule a build for the job on Jenkins

Related issues

Related to #9741 (closed)
Related to #16959

Original created by @segfault on 16059 (Redmine)

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