feat: #3636870 Provide a service to determine the CAPTCHA point that applies to a form

Julian Pustkuchenrequested to merge
issue/captcha-3636870:3636870-provide-a-captcha-point-determination-service into 2.x

Adds CaptchaService::getCaptchaPointForForm(), which returns the enabled CAPTCHA point for a form ID and optional base form ID (or the unsaved "enable globally" point), respects the "skip CAPTCHA" permission and the admin route setting, and collects the cacheability metadata of the result. captcha_form_alter() now uses it, so other modules (like Flag, #3636853) can find out whether a form shows a CAPTCHA without copying the lookup.

Co-Authored-By: Claude Opus 5.5 noreply@anthropic.com

Closes #3636870

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