Extract `changelog-check` to separate action

Nadie ha tomado este issue todavía.

The `changelog-check` workflow helps us ensure that changelogs are updated alongside changes in polyrepos and monorepos.

Currently, when we make use of this workflow in other repos we need to pin to a specific commit ID. This is cumbersome because it means that if we want to make a change to the workflow we now need to go through each repo by hand and update the commit ID.

If we extracted this workflow to an action, we could start using version strings such as `v1`. As long as new changes were backward compatible they would automatically get propagated to all of the repos.

Comienza localizando el workflow existente de changelog-check y revisando cómo lo consumen otros repositorios. Extráelo a una GitHub Action versionada, actualiza el modelo de uso para admitir referencias de estilo v1 y verifica que las comprobaciones de changelog sigan funcionando tanto para polyrepos como para monorepos.

Escrito por el modelo de indexación a partir del texto del issue.