integration-server-test: Add 9.0 to lazy rollover config

[ericywl]

Motivation/summary

apm-data plugin change in 9.0, i.e. 8.18 and 9.0 no longer share the same template: https://github.com/elastic/elasticsearch/pull/129418. Hence upgrading from 8.18 to 9.0 will have lazy-rollover.

How to test these changes

Run integration-server-test workflow: https://github.com/elastic/apm-server/actions/runs/15700651775.

[github-actions[bot]]

:robot: GitHub comments

Expand to view the GitHub comments

Just comment with:

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

[mergify[bot]]

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

• backport-7.17 is the label to automatically backport to the 7.17 branch.
• backport-8./d is the label to automatically backport to the 8./d branch. /d is the digit.
• backport-9./d is the label to automatically backport to the 9./d branch. /d is the digit.
• backport-active-all is the label that automatically backports to all active branches.
• backport-active-8 is the label that automatically backports to all active minor branches for the 8 major.
• backport-active-9 is the label that automatically backports to all active minor branches for the 9 major.