Improve code of SFTP back up flow

[mmorhun]

Is your task related to a problem? Please describe

Current flow is not optimal. We should improve it.

Describe the solution you'd like

Refactor code that is responsible for SFTP backup flow

Describe alternatives you've considered

No response

Additional context

No response

[mmorhun]

When I started looking into this issue, I found that SFTP backup mechanism is broken.
Short investigation showed that there are 3 problems (all is caused by random user ID in the Che Operator container):

1. User home is not writable (defined as /), so it fails to update ssh config in ~/.ssh folder. A quick fix is to add the following line in Dockerfile: env HOME=/tmp/
2. No ssh client in UBI image. To fix, just install openssh-clients package using microdnf install -y openssh-clients or add the package to already existing install command
3. ssh fails to open connection with the following error: No user exists for uid xxxx. This cause by absent record in passswd file. To fix, add write permissions for the /etc/passwd and add current user record in entrypoint script.

Edit: SFTP backup mechanism should be fixed by eclipse-che/che-operator#1271 , however it doesn't fix original issue

[tolusha]

WON'T FIX
Backup/Restore is flaky and doesn't works with DevWorkspace
Decommissioned by #21006