Test SNAPSHOT in smoketests

[carsonip]

Motivation/summary

Support "latest" in lagacy-managed and legacy-standalone-major-managed by testing snapshots.

Checklist

• Update CHANGELOG.asciidoc
• Documentation has been updated

For functional changes, consider:

• Is it observable through the addition of either logging or metrics?
• Is its use being published in telemetry to enable product improvement?
• Have system tests been added to avoid regression?

How to test these changes

(cd testing/smoke/legacy-standalone-major-managed && EC_API_KEY=redacted ./test.sh latest)
(cd testing/smoke/legacy-managed && EC_API_KEY=redacted ./test.sh latest)

Related issues

Part of #13051

[mergify]

This pull request does not have a backport label. Could you fix it @carsonip? 🙏
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.

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

[carsonip]

This should be tested again when 7.17 snapshot is fixed. Currently 7.17.22-SNAPSHOT is broken and APM doesn't start after upgrade to 8.x.

[simitt]

Currently 7.17.22-SNAPSHOT is broken and APM doesn't start.

Could you link to a tracking issue for this please?

[carsonip]

Currently 7.17.22-SNAPSHOT is broken and APM doesn't start.

Could you link to a tracking issue for this please?

The issue should be elastic/beats#39585

[carsonip]

I can confirm that the 7.17 build is fixed and both updated smoke tests now pass for latest.

[inge4pres]

👍🏼 thanks