Pkg/refactor

[manuGil]

This changes the location of the CLI module. Now this module is under the fairly module.
The new structure is as follows:

src
|_ fairly
    |_ cli
    |_ client
    |_ data
    ....

It also updates the entry point for the CLI in pyproject.toml, and includes a test to check if the CLI is reachable from the system's terminal.

This changes are part of the attempt to fix issues when preparing a package for conda forge conda-forge/staged-recipes#26158