content_history: redirect info should be dumped at page level

This MR changes when we perform enrichment on reconciliation events, and how we determine if an event will be enriched with redirect info.

Enrich with content and redirect only on insert and create changelog_kind.

Test if a page is a redirect by inspecting the response payload redirects key.

Determining redirect info at revision level is brittle. If the page id of the envent we want to enrich is a redirect, extend redirect data to all revisions.

This is consistent with Dumps v1.0 and mediawiki_wikitext_history behaviour.

Bug: T381040

cc / @xcollazo