sunpy 6.0 release candidate

[Nabil Freij]

Hello everyone!

The SunPy developers are pleased to announce the first release candidate for version 6.0 of the `sunpy` core library. If you develop a package that depends on `sunpy` we would strongly encourage you to test it with sunpy v6.0.0rc1, and report any issues you have on our issue tracker so we can fix them before the final release.

To install the release candidate use either:

`pip install sunpy==6.0.0rc1.post1`
`conda install -c conda-forge/label/sunpy_rc -c conda-forge sunpy`

[Headline features can be found on our what's new page](https://docs.sunpy.org/en/v6.0.0rc1/whatsnew/6.0.html) and [the full changelog is seperate](https://docs.sunpy.org/en/v6.0.0rc1/whatsnew/changelog.html#rc1-2024-07-12).

In summary:
- Decoupling dates in Map
- Removal of sunpy.database
- Removal of sunpy.net.helioviewer.HelioViewerClient
- Support for ADvanced Adaptive Prediction Technique (ADAPT)
- New PlanarScreen context manager

Many thanks!