[JENKINS-63905] Agent to controller rather than agent to master

[MarkEWaite]

JENKINS-63905 Terminology - Agent to controller, not agent to master

Update the terminology in the agent access control subsystem so that new screenshots can be taken to insert into the jenkins.io page at https://www.jenkins.io/doc/book/managing/security/#agentmaster-access-control or can be integrated into the new page proposed in PR-3353

Tested interactively to confirm that upgrade from Jenkins 2.249.2 worked as expected and that new install also worked as expected.

Proposed changelog entries

• Use 'Agent to controller' to describe agent access control system rather than 'agent to master'.

Proposed upgrade guidelines

N/A

Submitter checklist

• (If applicable) Jira issue is well described
• Changelog entries and upgrade guidelines are appropriate for the audience affected by the change (users or developer, depending on the change). Examples
  • Fill-in the Proposed changelog entries section only if there are breaking changes or other changes which may require extra steps from users during the upgrade
• Appropriate autotests or explanation to why this change has no tests
• For dependency updates: links to external changelogs and, if possible, full diffs

Maintainer checklist

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

• There are at least 2 approvals for the pull request and no outstanding requests for change
• Conversations in the pull request are over OR it is explicit that a reviewer does not block the change
• Changelog entries in the PR title and/or Proposed changelog entries are correct
• Proper changelog labels are set so that the changelog can be generated automatically
• If the change needs additional upgrade steps from users, upgrade-guide-needed label is set and there is a Proposed upgrade guidelines section in the PR title. (example)
• 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).

New screenshots for documentation

Enabling agent to controller access control

Define exceptions for agent to controller access

[res0nance]

Translations would probably need work.
The overall master -> Controller terminology would likely need an EPIC in jira as well to track all the required efforts but this is a great start

[oleg-nenashev]

All looks good, thanks @MarkEWaite !

We may merge it in 24 hours if there is no negative feedback. Please see the merge process documentation for more information about the merge process