Improve Pharmpy installation and setup

[rikardn]

• check-function (verbose=True)

• Find Python. Use reticulate.

• Check Python version >= 3.11 (built into pharmr) Print Python path

• Check if Pharmpy is available (reticulate::py_module_available)

• Check if Pharmpy version matches pharmr version

• Check if running in venv or not

• Block reticulate autoinstall

• Improve install_pharmpy

• Check Python version

• Improve setup of venv (first time). More control over reticulate

• Do not use conda?

• Run check-function

Python/Pharmpy installation cases:

1. To be installed in venv by install_pharmr
2. Installed into venv by user
3. System Python

[stellabelin]

Function check_setup() was added in cadbfde

[stellabelin]

In new reticulate version, auto install of virtual environment should be removed.