Move wheel repository to anaconda.org

[mhsmith]

This should give us better capacity and reliability than our current server, with a 24/7 support team behind it.

I created a chaquo organization and uploaded all the packages that were in the repository as of 2023-12-03. I also applied a pypi-7.0 label to those that should be visible to Chaquopy 13.0 and older.

But then I discovered that pypi.anaconda.org is serving packages from a different URL on every download, which makes pip's local cache useless and causes a noticeable performance regression. For example, an app that previously took 4 seconds to run the requirements task would now take 14 seconds. Internal issue link: https://anaconda.atlassian.net/browse/AS-1198

Once this is resolved, here's a a checklist for the remaining work:

• Turn pypi-7.0 and pypi-13.1 into redirects to https://pypi.anaconda.org/chaquo/label/pypi-7.0/simple/ and https://pypi.anaconda.org/chaquo/simple/ respectively. But first check that:
  • Both the oldest and newest Chaquopy version that uses the old URLs will follow redirects correctly.
• Update server/pypi/README-internal.md with upload instructions.
  • And keep uploading to the existing server as a backup, just like https://chaquo.com/maven-central.
• Update Gradle plugin to use anaconda.org URL
• Update links in documentation and issue tracker, including BeeWare, to point at https://anaconda.org/chaquo/repo?sort=_name&sort_order=asc.