Delete all versions throws 504 Gateway Timeout on projects with large amount of versions

[Zlopez]

When trying to use Delete versions button on project with large amount of versions the task throws 504 Gateway Timeout.

The project that this was discovered on is cataclysm-dda.

The task will be done anyway, but the frontend will timeout in the meantime.

[Zlopez]

It seems that this method needs better optimization, it is deleting the versions one by one and it also publishes a message after each deleted version, which is probably the bottleneck.

We should either add a new topic or update the current one to support multiple versions removed at once. The second option will be probably better.