Add a friendly explanation to Timed Out workspaces

Is your feature request related to a problem? Please describe

When a workspace is left open in a browser tab but not used for half an hour it gets timed out.
When the user finally returns to that workspace tab, instead of seeing Gitpod's VSCode interface, they get this intimidating screen -

Describe the behaviour you'd like

It would be a great improvement to make this screen friendly.
We can add a message, like:
"Gitpod workspaces get timed out after 30 minutes of no activity.
No worries, everything you worked on was securely saved.
To continue working please click on Open Workspace button".

If it's possible to keep a blurry version of VSCode interface in the background, and add this message on top, it would be even better, because users would be less surprised and more familiar with how the screen looked like the last time they were on.

Describe alternatives you've considered

Additional context

This is somehow related to loading new workspaces, https://github.com/gitpod-io/gitpod/issues/3738, where the interface should be improved with information about what is happening, what to expect, and how long they might wait (sometimes over a minute)

Start by finding the UI shown when a workspace has timed out, using the screenshots and the related workspace-loading issue #3738 as context. Done means the timeout screen clearly explains the 30-minute timeout, reassures users that their work was saved, and tells them how to reopen the workspace.