ZTS: Remove functional tests via matrix

This commit changes the workflow of the github actions.

• Ubuntu 20.04, 22.04, 24.04 will be tested via QEMU now
• remove unused scripts of this commit: b7bc334d1
• re-add the zloop standalone testings via zloop.yml

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Signed-off-by: Tino Reichardt <milky-zfs@mcmilk.de>
Closes #16549