simplify remote executor

[jsonar-cpapke]

Related to https://onejira.imperva.com/browse/SD-1064

Standardize getting paramiko client. Create remote_client_context to return a client with or without proxy, and cleanup afterwards.

As well, added some raise from to improve debugging.

This is the prequal to using the paramiko client for more things, so simplifying how to create one is important.

[jsonar-cpapke]

I see a failure with create terraform that seems unrelated to these changes

[lindanasredin]

I see two actions failed, one failure in DAM so not related: https://github.com/imperva/dsfkit/actions/runs/7876864234/job/21491779160#step:21:10113
And one failure in upgrade in the unit tests: https://github.com/imperva/dsfkit/actions/runs/7876864231/job/21491778541#step:7:1405
The error is:
ERROR tests/test_main.py::test_main_raise_exception_on_overall_status_failed - AttributeError: <module 'upgrade.main' from '/home/runner/work/dsfkit/dsfkit/modules/aws/sonar-upgrader/python_upgrader/upgrade/main.py'> does not have the attribute 'test_connection'

This looks related to the change.

[jsonar-cpapke]

@lindanasredin I've already fixed and rerun those tests https://github.com/imperva/dsfkit/actions/runs/7877609163