Ci cleanup scripts

Ben Boeckelrequested to merge
ben.boeckel/cmb-superbuild:ci-cleanup-scripts into master

Currently running a dry-run of the DockerHub cleaning. GDrive reports this:

To-delete bundles size: 289195817728 bytes (270G)
Preserved bundles size: 34364590218 bytes (33G)

DockerHub report:

To-delete images size: 6552110149277 bytes (6.0T)
Preserved images size: 74349397291 bytes (70G)
Edited by Ben Boeckel

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