Move release process steps into CI
Numerous steps from the release process can be moved into the CI pipeline. Of note:
- creating source and documentation tarballs (!8128 (merged))
- uploading documentation and source tarballs to vtk.org
- uploading documentation to vtk.org (not nightly, but a versioned directory)
- uploading wheels to VTK's package registry (!8128 (merged))
- creating a release on VTK's repository
- uploading assets to VTK's repository and linking them to the release
For prior art on uploading assets and creating releases, the CI jobs in the
ci-utilities repository can be used.
The release process checklist should be updated to reflect these changes.