[Feature] Remove pypowsybl from main dependencies

[RalfCortes]

While pypowsybl is obviously required to use pypowsybl2grid, having pypowsybl-rte installed in the same environment can cause issues. Specifically, pypowsybl2grid attempts to install pypowsybl, which will fail because pypowsybl and pypowsybl-rte are incompatible and cannot coexist..

Solution : move pypowsybl to dev dependencies and add maybe a flag to make this work :

pip install pypowsybl2grid[rte]
# or
pip install pypowsybl2grid[default]

At the same time we could also move towards uv for the dependencies management.