helpers: install as setuptools scripts

[hundeboll]

Allow using e.g. labgrid-count-connect also when installing labgrid using pip.

Description
We install labgrid using pip in a Containerfile, but need to use labgrid-bound-connect on the exporter. This isn't currently possible, as the two scripts in ./helpers/ aren't installed unless building a debian package.

To make it possible to configure the two helpers as scripts in pyproject.toml they must reside in the python package itself, so move the two files from ./helpers/ to ./labgrid/helpers.

Both scripts are also changed to configure/parse arguments in a function instead of the global scope, as the setuptools scripts configuration needs to call a function from the specified files.

Checklist

• Documentation for the feature
• Tests for the feature

• The arguments and description in doc/configuration.rst have been updated

• Add a section on how to use the feature to doc/usage.rst

• Add a section on how to use the feature to doc/development.rst

• PR has been tested

• Man pages have been regenerated