Classic bundled themes: Border support tracking issue

[poena]

This tracking issue replaces https://core.trac.wordpress.org/ticket/55974, with blessing from the testing team, because the original ticket was becoming too difficult to follow.

The classic bundled themes are missing support for border options for blocks.
The border options include border color, width, style, and radius.

The options should be enabled by adding add_theme_support( 'border' ); to theme's setup function in functions.php.

There are other methods that could be used, but they enable more features than the border options.
By using this theme support, the scope of the task can be limited to the borders.

Each classic bundled theme should be updated using a separate Trac ticket and pull request.
The previous ticket showed that the conversation easily got out of hand when many themes were discussed at the same time.

The respective Trac tickets will be listed here once they are opened.

Status

Twenty Ten:
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Twenty Twenty-One: https://core.trac.wordpress.org/ticket/63075

[poena]

#55974 was marked as a duplicate.

[karmatosed]

Let's get a testing label on this if a request from testing team.

[SirLouen]

Replying to karmatosed:

Let's get a testing label on this if a request from testing team.

According to @poena each theme (or group of themes) might have its/their own report and testing instructions. I think that needs-testing doesn't apply here because there is nothing implicit to test afaik.