Implement/extend transport plugin to support authentication by password while not recommending it

[agoscinski]

Is your feature request related to a problem? Please describe

A number of French HPCs only allow an authentication by password. By modern safety standards this is considered as not safe but it is current state for a lot of HPCs (merde!) so we should support it while not recommending it. Since this is a large user bases I marked it as important.

Describe the solution you'd like

Implement a transport plugin or extend the current transport to also support ssh connections authenticated by password.

[unkcpz]

I think it would be better to not put in the aiida-core but as a separate plugin and registered in aiida-register?

[khsrali]

I can arrange this in core.ssh_async or to be unified with core.ssh
We can put it in the aiida-core, but explicitly warn them about the danger of this unsafe behavior.. the rest is user's responsibility tbh..