Supported releases GUI is confusing for semantic versioning [#3204263]

Problem/Motivation

This started a question on Drupal answers.

With the old versioning system, the supported setting applied to each major version. With semantic versioning, it applies to each minor version. This seems to be creating confusion and making unnecessary work for site admins.

@kiamlaluno made the following comments.

For example, on the screenshot I took, there are three series (2.1.*, 2.0.*, and 2.*), but the Git branch seems just one (2.x).

I am not sure it's correct to make maintainers mark a 2.0.0 version as unsupported, and mark version 2.1.0 as supported, while the same is not possible for 8.x-1.1 and 8.x-1.0. In that screenshot, marking the 8.x-1.* serie as unsupported would mean to mark both versions as unsupported, not just one of them.

Also, it's probable the maintainer deselected Supported for 2.0.* because the user interface was showing both the 2.1.0 and 2.0.0 versions on the project page, which is not something he expected. It could be he just wanted to hide the 2.0.0 version, and that is the only way he found to achieve it. Unfortunately, the consequence was sending emails to users who are using the 2.0.0 version.