Prepare to migrate SH users to SSH Gateway in VS Code Desktop

[akosyakov]

To address blocked users we are going, i.e. Error: Timed out while waiting for handshake error:

• increase handshake timeout for bad connections
• show a warning about possible blocked SSH port and suggest to continue with the deprecate tunneling over WebSocket

We should also:

• fix a warning notification by blocking a user flow if the installation does not have configured SSH keys before falling back to the deprecated mode
• and add gitpodHost property to ConfigCat that we can control traffic shift separately for SaaS and SH installations