Replace container-inline with form--inline to display forms horizontally.

The Needs Review Queue Bot → tested this issue. It either no longer applies to Drupal core, or fails the Drupal core commit checks. Therefore, this issue status is now "Needs work".

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Gauravvvv → changed the visibility of the branch 2417111-replace-container-inline-with to hidden.

MR has failures.

Still seeing patches

Issue summary should be reviewed as it has been 8 years.

Haven't read all the comments.

Adding 📌 Refactor system/base library Needs work as parent, ideally we'd only load this CSS where it's needed on forms, and remove it from the global system/base library too.