Drupal core translation status page is missing

Problem/Motivation

The Drupal 7 drupal.org connector provides translate/drupal_core, the "Drupal core translation status" page: every language with its progress on the newest stable (or release candidate) Drupal core release and its contributor count, linked to the untranslated strings of that release, sorted by progress. 3.0.x has no such page.

Steps to reproduce

Proposed resolution

Port it into the l10n_drupal_rest connector: a route at translate/drupal_core for users with access localization community, a controller that picks the newest core release that is neither alpha nor beta and shows the packager counts of that release. The table itself is the one the welcome page already builds for the highlighted project, so that code moves into a shared builder in l10n_community (L10nProjectOverview::buildStatusTable()), used by both pages; the connector now depends on l10n_community, which Drupal 7 did implicitly by loading its include file.

Tests: new Drupal 7 test testDrupalCoreStatus() in the rest connector test (three core releases, one of them beta, packaged translations, the status line, the progress header, the language link with the release filter, the progress percentage) and its port DrupalCoreStatusTest.

Remaining tasks

User interface changes

API changes

Data model changes

LLM disclosure

LLM was used to find, diagnose explain and fix this issue. With human review.