[policy, no patch] set miminum composer.json version constraints based on first minor release

Possible text for https://www.drupal.org/about/core/policies/core-dependency-policies-and-... →

Major release

The version constraints for all components in core/composer.json are set to the minimum version in core/composer.lock during the RC phase.

This reduces the number of versions of a dependency supported and therefor reduces the number of valid versions of a dependency that are potential solutions from the Composer resolver.

I recently learned composer bump is a potentially useful command for this.