Allow users to always download the latest available workspace backup

[atduarte]

Is your feature request related to a problem? Please describe

Currently, users are only able to download the backup of their workspace when it's stopped. This is a problem particularly if the workspace gets stuck in the Stopping state.

Describe the behaviour you'd like

As a user I would like to always be able to download the latest backup. Even if it doesn't represent the latest state.

Describe alternatives you've considered

Remaining as is.

Additional context

This idea came up while the workspace team discussed how durability and accessibility of backups could be improved. Efforts are being made by the team to improve durability [1].

[jldec]

@atduarte there is already an issue / discussion about this in #4977

• new running workspaces have no backup, so the Download link should be disabled. Currently it is there, but leads to an error page.
• any workspace which has been stopped at least once has a working Download link, which downloads the most recent backup, even when the workspace is running.

[atduarte]

@jldec Perfect! Have to improve my Github search skills 😅 Will close this issue.

Just a minor difference: If the workspace is stopping for the first time, the backup might or might not have happened. In the cases that it happened, the backup should be available to the user.