camkes-cli is out of date

[lsf37]

The camkes-cli tool is unused and basically bit-rotted.

It should either be resurrected and brought up to date (might not be hard), or be retired/put on hold officially.

The tool is on pypi and mentioned on https://docs.sel4.systems/projects/camkes/cli

There is a test-action for it in seL4/ci-actions#87, but that is on hold until this issue is decided.