Enhance module imports in NEST Server

[babsey]

This PR converts environment variable NEST_SERVER_MODULES:
NEST_SERVER_MODULES="nest,numpy as np,random from numpy"
to formatted dictionary for updating globals:
{'nest': <module 'nest'> 'np': <module 'numpy'>, 'random': <module 'numpy.random'>}

Test it on your computer

In Bash:

export NEST_SERVER_MODULES="nest,numpy as np,random from numpy"

In Python:

import nest
modules = nest.server.hl_api_server.get_modules_from_env()
globals().update(modules)
print(globals())

[jougs]

There seems to be some formatting issues with the new code. I'm still approving.

[github-actions]

Pull request automatically marked stale!

[babsey]

The test failed because of NEST CI / black.
I do not understand the reason of the error.

Please clarify.

[Helveg]

The NEST CI / black is a Python source code formatting check. Please install and apply black, or install the autoformatting pre-commit hook, as outlined here

[jougs]

Not sure where my previous approval went, but I'm still happy.

[jougs]

@Helveg: can you please have a look? Thanks!

[Helveg]

@babsey what do you think about using the stdlib AST for this parsing task?

[babsey]

It looks fine. Please review! 😄