Delete pending release confirmation if the tag is removed

[dd32]

When a plugin has Release Confirmations enabled, if the tag is deleted before the request is confirmed, the release remains in the plugin admin showing as "release confirmation needed".

When a tag is removed, it should remove any pending confirmations.

Potentially, the release should remain in the list, just marked as 'deleted' or 'removed'.

Additionally, it would be beneficial if there was an Admin UI for plugin reviewers to remove/block/disable/something pending confirmations for plugins.
This would be used in the event that either

• A bug occurs (such as this tickets cause) or
• In the event that a plugin author were to contact the team with a "Don't release that!!" - there needs to be some way to ignore/discard the pending release.

[dd32]

Additionally, it would be beneficial if there was an Admin UI for plugin reviewers to remove/block/disable/something pending confirmations for plugins.

This was implemented via [12813], plugin authors also have access to it.

[dd32]

In 13709:

Plugin Directory: SVN: Watch for Tag deletions, such that we can properly handle cases when a tag is deleted.

See #3263, #5900.

[dd32]

In 13711:

Plugin Direcrory: When Release Confirmation is enabled, and a tag for a non-confirmed release is deleted, remove the release.

Fixes #5900.