Drop support for remoting releases before 2024-08

[daniel-beck]

The fix for SECURITY-3430 retains compatibility with older remoting releases to have a smoother upgrade experience. This PR drops that support. It's probably going to be a while before we want to merge this, but I thought it would be useful to have this prepared.

Testing done

Autotests

Proposed changelog entries

• Drop support for Remoting (agent.jar) releases from before August 2024.

Proposed upgrade guidelines

(Copied from #9440 for consistency)

Increase the minimum required Remoting version to 3256.3258.v858f3c9a_f69d (released on August 7, 2024). When an agent with a Remoting version older than 3256.3258.v858f3c9a_f69d connects to the Jenkins controller, the agent connection is rejected. Ensure that all agents are running a recent version of Remoting prior to upgrading. Agents with unsupported Remoting versions can be allowed to connect to the controller by setting the hudson.slaves.SlaveComputer.allowUnsupportedRemotingVersions system property to true.

Submitter checklist

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1. The Jira issue, if it exists, is well-described.
2. The changelog entries and upgrade guidelines are appropriate for the audience affected by the change (users or developers, depending on the change) and are in the imperative mood (see examples). Fill in the Proposed upgrade guidelines section only if there are breaking changes or changes that may require extra steps from users during upgrade.
3. There is automated testing or an explanation as to why this change has no tests.
4. New public classes, fields, and methods are annotated with @Restricted or have @since TODO Javadocs, as appropriate.
5. New deprecations are annotated with @Deprecated(since = "TODO") or @Deprecated(forRemoval = true, since = "TODO"), if applicable.
6. New or substantially changed JavaScript is not defined inline and does not call eval to ease future introduction of Content Security Policy (CSP) directives (see documentation).
7. For dependency updates, there are links to external changelogs and, if possible, full differentials.
8. For new APIs and extension points, there is a link to at least one consumer.

Desired reviewers

@mention

Before the changes are marked as ready-for-merge:

Maintainer checklist

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1. There are at least two (2) approvals for the pull request and no outstanding requests for change.
2. Conversations in the pull request are over, or it is explicit that a reviewer is not blocking the change.
3. Changelog entries in the pull request title and/or Proposed changelog entries are accurate, human-readable, and in the imperative mood.
4. Proper changelog labels are set so that the changelog can be generated automatically.
5. If the change needs additional upgrade steps from users, the upgrade-guide-needed label is set and there is a Proposed upgrade guidelines section in the pull request title (see example).
6. If it would make sense to backport the change to LTS, a Jira issue must exist, be a Bug or Improvement, and be labeled as lts-candidate to be considered (see query).

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[github-actions]

Please take a moment and address the merge conflicts of your pull request. Thanks!

[github-actions]

Please take a moment and address the merge conflicts of your pull request. Thanks!

[github-actions]

Please take a moment and address the merge conflicts of your pull request. Thanks!