XWIKI-24563: The URL input in the link edition picker is not keyboard focusable

[Sereza5]

Jira URL

https://jira.xwiki.org/browse/XWIKI-24563

Changes

Description

• Added the logic to handle the tabindex like it used to be done when we used selectize in the back.

Clarifications

• See ticket for explanation of the issue. The fix is straightforward once we understand why this issue appeared.

Screenshots & Video

# Executed Tests

Semi manual tests with Claude code (see comparison above made from the local instance).

Built the changes with mvn -q clean install -pl xwiki-platform-core/xwiki-platform-web/xwiki-platform-web-war -Plegacy,snapshot -DskipTests -Dxwiki.checkstyle.skip=true -Dxwiki.revapi.skip=true -Dxwiki.surefire.captureconsole.skip=true.

Ran the docker tests: mvn clean verify -pl xwiki-platform-core/xwiki-platform-appwithinminutes/xwiki-platform-appwithinminutes-test/xwiki-platform-appwithinminutes-test-docker -Pintegration-tests,docker,legacy,snapshot -Dtest=UserClassFieldIT -DfailIfNoTests=false -Dxwiki.checkstyle.skip=true -Dxwiki.revapi.skip=true -Dxwiki.surefire.captureconsole.skip=true

There was one fail here, but it was unrelated to the change (could reproduce it after reverting the changes from this PR).

Expected merging strategy

• Prefers squash: Yes
• Backport on branches:
  • None. The cause was merged back in 18.2.0-rc1 so we definitely don't want to backport any further than that.