[7.17](backport #29032) CI: add GitHub actions for macos (push based)

[mergify]

This is an automatic backport of pull request #29032 done by Mergify.

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Mergify commands and options

More conditions and actions can be found in the documentation.

You can also trigger Mergify actions by commenting on this pull request:

• @Mergifyio refresh will re-evaluate the rules
• @Mergifyio rebase will rebase this PR on its base branch
• @Mergifyio update will merge the base branch into this PR
• @Mergifyio backport <destination> will backport this PR on <destination> branch

Additionally, on Mergify dashboard you can:

• look at your merge queues
• generate the Mergify configuration with the config editor.

Finally, you can contact us on https://mergify.com

[botelastic]

This pull request doesn't have a Team:<team> label.

[elasticmachine]

💚 Build Succeeded

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• Start Time: 2022-01-13T18:01:03.659+0000

• Duration: 17 min 0 sec

• Commit: 7ed1886

❕ Flaky test report

No test was executed to be analysed.

🤖 GitHub comments

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

• /test : Re-trigger the build.

• /package : Generate the packages and run the E2E tests.

• /beats-tester : Run the installation tests with beats-tester.

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