Remove obsolete CI/testing scripts

In rationalising and updating the CI system, it's good to have a clear out of obsolete or otherwise never touched functionality. None of the removed scripts are observed to be used in any testing/CI scripts, and haven't been touched/updated in recent years. If they are still required, we can easily restore, but better would be to reimplement with proper tests/use.

The changes here will not impact any ongoing sprint work. They could also be backported to the v1 patches branch, but it's not a requirement until we make longer term changes to the CI to support that on the patches branch.