[Sync EN] Refactor filter constants by splitting into separate files (#5886)

[github-actions]

Commit: https://github.com/php/doc-en/commit/a109099b7deda187b68d43d8a90393620eaeb8e1
PR: https://github.com/php/doc-en/pull/5886

Fichiers FR à mettre à jour

• reference/filter/constants.xml

Nouveaux fichiers EN (pas encore traduits)

• reference/filter/constants.callback.xml
• reference/filter/constants.flags.generic.xml
• reference/filter/constants.flags.sanitization.xml
• reference/filter/constants.input.xml
• reference/filter/constants.sanitization.xml
• reference/filter/constants.validation.xml