transport.compress and transport.extract

[khsrali]

We plan to develop more types for StashMode such as zip or tar, etc.
Also potentially an unstashing feature that could "undo" whatever stashing did.

For that we need to develop function execmanager.py::stash_calculation to compress a list of paths starting from a common root.
Once can simply use transport.exec_command_wait, however aiida-firecrest does not and will not support that.

So now that we know that, and that we are in early stage of developing this feature, I suggest we keep that in mind, and introduce features like transport.compress and transport.extract.
So that the action of compressing and extracting is left to the hands of the transport plugin. It's up to transport plugin how to handle that, either by executing a command or sending a REST request.

In my opinion this makes a lot of sense. Also in general, we may need to have the codebase interface as independent as possible from transport.exec_command_wait.
So execmanager.py::stash_calculation would only call on transport.compress and transport.extract without being bothered by how is that done.

discussed with @agoscinski