upgrade min jenkins core and plugins versions

[haugenj]

Upgrades the Jenkins core version from 2.112 to 2.222.4. Many other plugins will not work with core versions less than 2.222.4 anymore, for example this is causing an error here: https://github.com/jenkinsci/ec2-fleet-plugin/pull/273/checks?check_run_id=3352856751

Also upgrades the plugins version too

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(edit)
Ended up having to expand the scope of this change:

• upgraded core to 2.235.5 after seeing this on the Jenkins website:

  Do not use versions no longer supported by the update center, which is currently anything older than 2.243 for weekly releases, and 2.235.2 for LTS releases.

• Added the Jenkins Core BOM (https://github.com/jenkinsci/bom) to help manage dependency versions

• Stripped the "LTS" builds out of the Jenkinsfile because they failed to build and I didn't see a recommendation that it needed to be used (https://github.com/jenkins-infra/pipeline-library)

• Updated the developers list to an accurate state

• Updated tests to remove deprecated API

• Updated UI tests to support new UI location for clouds

and for extra credit (because they caused the builds to fail randomly on jenkins.io)

• Modified the EC2RetentionStrategyIntegrationTest tests to manually trigger the idle checks, since they would not always get called

[haugenj]

only took a few tries...

[imuqtadir]

lgtm! thanks for fixing the tests. Ideally would have liked if you opened two PRs for your changes — version change and fixing tests 👀