[9.0](backport #6578) Fix selection of testing version

[mergify]

SLightly changing algorithm to select test versions

with config

{
  "UpgradeToVersion": "9.0.0",
  "CurrentMajors": 1,
  "PreviousMajors": 1,
  "PreviousMinors": 2,
  "SnapshotBranches": [
    "8.x",
    "8.17",
    "7.17"
  ]
}

these available versions

-8.16.3
-8.17.1
-7.17.27
-8.16.2
-8.17.0
-7.17.26
-8.15.5
-8.16.1
-8.16.0
-8.15.4
-8.15.3+build202411051926
-7.17.25
-and so on

resolved to

before change:

  - 8.18.0-SNAPSHOT
  - 8.17.1
  - 8.17.1-SNAPSHOT
  - 8.17.0
  - 7.17.28-SNAPSHOT

after change:

  - 8.18.0-SNAPSHOT
  - 8.17.1
  - 8.17.1-SNAPSHOT
  - 8.16.3
  - 7.17.28-SNAPSHOT

as we wanted 1 previous major in case of target 9.0.0 it is 8.x
and 2 previous minors so out of 8.x we took latest patches for 8.17 and 8.16 as released ones

---

This is an automatic backport of pull request #6578 done by Mergify.

[elasticmachine]

Pinging @elastic/elastic-agent-control-plane (Team:Elastic-Agent-Control-Plane)

[elastic-sonarqube]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarQube

[elasticmachine]

💔 Build Failed

• Buildkite Build
• Commit: c1e0cf0

Failed CI Steps

• null

cc @michalpristas

[jlind23]

Airgapped issues are known but what about this one?

log_level_test.go:219: agent status: {"info":{"id":"19d79202-d19e-457b-b559-68445e8c087d","version":"9.0.0","commit":"c1e0cf02e493e8f6754eeaee553ee3c9fe1b8bcf","build_time":"2025-02-25 20:21:01 +0000 UTC","snapshot":true,"pid":73252,"unprivileged":true},"state":5,"message":"Re-executing","components":[{"id":"beat/metrics-monitoring","name":"beat/metrics","state":2,"message":"Healthy: communicating with pid '73323'","units":[{"unit_id":"beat/metrics-monitoring","unit_type":1,"state":0,"message":"Starting","payload":{"osquery_version":""}},{"unit_id":"beat/metrics-monitoring-metrics-monitoring-beats","unit_type":0,"state":0,"message":"Starting","payload":{"osquery_version":""}}],"version_info":{"name":"beat-v2-client","version":"","meta":{"build_time":"2025-02-25 13:05:29 +0000 UTC","commit":"e863252dcf33987eb8e6d19d5c48df390fb3e60c"}}},{"id":"filestream-monitoring","name":"filestream","state":2,"message":"Healthy: communicating with pid '73311'","units":[{"unit_id":"filestream-monitoring","unit_type":1,"state":0,"message":"Starting","payload":{"osquery_version":""}},{"unit_id":"filestream-monitoring-filestream-monitoring-agent","unit_type":0,"state":0,"message":"Starting","payload":{"osquery_version":""}}],"version_info":{"name":"beat-v2-client","version":"","meta":{"build_time":"2025-02-25 13:05:29 +0000 UTC","commit":"e863252dcf33987eb8e6d19d5c48df390fb3e60c"}}},{"id":"http/metrics-monitoring","name":"http/metrics","state":0,"message":"Starting: spawned pid '73337'","units":[{"unit_id":"http/metrics-monitoring","unit_type":1,"state":0,"message":"Starting: spawned pid '73337'","payload":{"osquery_version":""}},{"unit_id":"http/metrics-monitoring-metrics-monitoring-agent","unit_type":0,"state":0,"message":"Starting: spawned pid '73337'","payload":{"osquery_version":""}}],"version_info":{"name":"","version":"","meta":{"build_time":"","commit":""}}},{"id":"system/metrics-default","name":"system/metrics","state":2,"message":"Healthy: communicating with pid '73299'","units":[{"unit_id":"system/metrics-default","unit_type":1,"state":2,"message":"Healthy","payload":{"osquery_version":""}},{"unit_id":"system/metrics-default-unique-system-metrics-input","unit_type":0,"state":2,"message":"Healthy","payload":{"osquery_version":""}}],"version_info":{"name":"beat-v2-client","version":"","meta":{"build_time":"2025-02-25 13:05:29 +0000 UTC","commit":"e863252dcf33987eb8e6d19d5c48df390fb3e60c"}}}],"collector":null,"FleetState":6,"FleetMessage":"Not enrolled into Fleet","upgrade_details":null}
--
  | fixture.go:665: >> running binary with: [/opt/Elastic/Agent/elastic-agent status --output json]
  | log_level_test.go:210: error fetching agent status: could not unmarshal agent status output: invalid character 'E' looking for beginning of value
  | exit status 1:
  | Error: failed to communicate with Elastic Agent daemon: rpc error: code = Unavailable desc = connection error: desc = "transport: Error while dialing: dial unix /opt/Elastic/Agent/elastic-agent.sock: connect: connection refused"