Migrate Commons Lang from 2 to 3 and StringEscapeUtils to Commons Text

[timja-bot]

Migrate from deprecated/EOL Commons Lang 2 to Commons Lang 3, and StringEscapeUtils to Commons
Text. This repository was previously using an inconsistent mix of versions — much of the code
already imports org.apache.commons.lang3.

Part of the effort to remove Commons Lang 2 from Jenkins core — jenkinsci/jenkins#16404,
jenkinsci/jenkins#26105. Commons Lang 2 is EOL and carries an unfixed advisory
(GHSA-j288-q9x7-2f5v).

What's changed

• Renamed the remaining org.apache.commons.lang.* imports to org.apache.commons.lang3.* and
  declared io.jenkins.plugins:commons-lang3-api explicitly instead of relying on a transitive copy.
• StringEscapeUtils.escapeJava moves to org.apache.commons.text.StringEscapeUtils via
  commons-text-api — Lang 3's copy is itself deprecated, so this goes straight to Commons Text.
• abbreviate / isEmpty / isNotBlank / trimToEmpty behave identically in Lang 3.

Testing done

mvn -B -ntp clean verify passes locally on Java 21 / macOS.

The ban-commons-lang-2 enforcer rule was left disabled: it needs parent POM
6.2116.v7501b_67dc517 or newer, and parent 6.x requires Jenkins 2.475+ (Jakarta EE 9) while this
plugin targets 2.414.3 — the POM does not resolve with the newer parent. Worth enabling after a
Jakarta migration.

Submitter checklist

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests that demonstrate the feature works or the issue is fixed

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🤖 This pull request was generated with AI assistance (Claude Code) as part of a bulk migration
across Jenkins plugins. If anything here looks wrong, please comment on this PR or contact @timja.

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This change is