getBranchesFromAliases step to avoid duplicated code

[v1v]

What does this PR do?

getBranchesFromAliases step to replace the code in some pipelines:

• https://github.com/elastic/apm-server/blob/main/.ci/schedule-daily.groovy#L34-L63
• https://github.com/elastic/beats/blob/9d26aea48d4dcf14f146b8a328f5b463c5cfa12d/.ci/schedule-daily.groovy#L34-L67

Why is it important?

DRY

[apmmachine]

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• Start Time: 2022-02-15T21:21:36.633+0000

• Duration: 11 min 53 sec

Test stats 🧪

Test	Results
Failed	0
Passed	1360
Skipped	2
Total	1362

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