current installation instructions re: spack are out-of-date compared to the available spack packages

[Noerr]

Description

The latest WarpX installation instructions specific to using spack reference py-warpx package. I find this information to be stale after 2023 as the py-warpx package was deprecated in 2024.

System information

• Operating system (name and version): Ubuntu 22.04 LTS
• Version of WarpX: 24.10
• Installation method: Spack
• Other dependencies: no
• Computational resources: CPU

If applicable, please add any additional information about your software environment:
Spack 0.23.0

Additional information

py-warpx spack package is limeted to the 2023.08 tag. Deprecation messages in the source code suggest the modern way to do this. Recommended changes to documentation source https://warpx.readthedocs.io/en/latest/_sources/install/users.rst.txt are below.

Using the Spack Package
-----------------------

Packages for WarpX are available via the `Spack <https://spack.readthedocs.io>`__ package manager.
The package ``warpx`` installs executables and allows for optional Python bindings, i.e. `PICMI <https://github.com/picmi-standard/picmi>`_.

.. code-block:: bash

   # optional: activate Spack binary caches
   spack mirror add rolling https://binaries.spack.io/develop
   spack buildcache keys --install --trust

   # see `spack info warpx` for build options.
   # optional arguments:  -mpi ^warpx dims=2 compute=cuda
   spack install warpx +python
   spack load warpx

See ``spack info warpx`` and `the official Spack tutorial <https://spack-tutorial.readthedocs.io>`__ for more information.

Relevant Slack thread: https://ecpwarpx.slack.com/archives/C3QACPQLT/p1736962799412309

[ax3l]

Thanks for raising this issue! Yes, let's update our documentation on this, thanks!

We have also a PR to Spack open that removes the old package py-warpx in favor of warpx +python. I opened it in October before my parental leave and it looks nobody pushed it further, so I just came back to it now that I am back :)

[ax3l]

Updating the docs in #5587 -- thanks a lot for the report @Noerr ! 🙏

Let us know if you encounter any other issues with the install in fresh issues!