chore: #3634582 Release 8.0.0-rc1

AI Yasrequested to merge
issue/cloud-3634582:3634582-release-8.0.0-rc1 into 8.x

Prepare Cloud 8.0.0-rc1 with Drupal 10.6 and 11.4 support. Update version references, resolve Drupal 11.4 compatibility and deprecations, and split the PHPUnit suite across four CI jobs.

Tested on Drupal 10.6.20 and 11.4.11. Composer, PHPCS, PHPStan, ESLint, stylelint, and all PHPUnit shards passed.

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