ssh module refactoring separate auth/shell checks

[nikaiw]

This pull request aims to refactor the code to make it more readable but also to properly separate the code that can be linked to authentication from the code linked to the test concerning the shell obtained

[NeffIsBack]

While we are at it we should probably also catch the timeout error in #358.

[NeffIsBack]

@nikaiw any update on this?

[nikaiw]

hello @NeffIsBack sorry this was sitting in my dev folder for a while. I'm not sure what I wanted to double check before commiting

[NeffIsBack]

While i think the current implementation is not ideal, this PR introduces way too many problems with private key authentication, which work in the main branch. I tried fixing them in the last hour, but at this point i will need to refactor the implementation anyways.

I will continue working on ssh in #531, but closing this one for now. Still thanks for your work, i will implement some ideas in the new PR!