ci: support for next patch release branch 8

[v1v]

Motivation/summary

7 major branch is only about 7.17, while the 8 major branch supports now:

• 8.0
• 8.1

Update the daily jobs to use the right aliases since 7 major won't have any further minor releases.

Issues

Requires elastic/apm-pipeline-library#1548

[apmmachine]

💚 Build Succeeded

the below badges are clickable and redirect to their specific view in the CI or DOCS

Expand to view the summary

Build stats

• Start Time: 2022-02-15T09:49:36.707+0000

• Duration: 55 min 55 sec

Test stats 🧪

Test	Results
Failed	0
Passed	5635
Skipped	19
Total	5654

🤖 GitHub comments

To re-run your PR in the CI, just comment with:

• /test : Re-trigger the build.

• /hey-apm : Run the hey-apm benchmark.

• /package : Generate and publish the docker images.

• run elasticsearch-ci/docs : Re-trigger the docs validation. (use unformatted text in the comment!)

[mergify]

This pull request does not have a backport label. Could you fix it @v1v? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-7.x is the label to automatically backport to the 7.x branch.
• backport-7./d is the label to automatically backport to the 7./d branch. /d is the digit

NOTE: backport-skip has been added to this pull request.

[v1v]

I just refactored this implementation in order to consume a new step in the library elastic/apm-pipeline-library#1548

I need to cut a new release to benefit from this refactorization.

[v1v]

Tests

It works now

[axw]

🎉 Thank you @v1v!