Update behavior of inmanta module install

[wouterdb]

Temporarily blocked on the outcome of this Slack discussion

as follow up to #6655

Update the pip config used by inmanta module install to behave as follows:

1. raise an error stating that the command is no longer supported.
2. Offer the suggestion to run pip install -e . to install a module in development mode
3. Offer the suggestion to run inmanta module build followed by pip install if the user really does not want an editable install.
4. The inmanta module build command should use use-system-config=true. It is assumed safe because it only installs build dependencies.

Tasks

• implement behavior as described above
• update docs