Make tests requiring iso with payload (DVD iso) reliable running in reasonable time (reduce DVD fetch time)

[rvykydal]

We are seeing s lot of flakes on Fedora where we are using Server DVD:
#694

For RHEL the production DVD is huge (~9 GB), the download time exceeds the test timeout.

These tests are involved:
https://github.com/rhinstaller/kickstart-tests/blob/master/harddrive-install-tree.sh - disabled on RHEL
https://github.com/rhinstaller/kickstart-tests/blob/master/harddrive-install-tree-relative.sh - disabled on RHEL
https://github.com/rhinstaller/kickstart-tests/blob/master/harddrive-iso.sh - disabled by not being executable
https://github.com/rhinstaller/kickstart-tests/blob/master/repo-addrepo-hd-tree.sh - disabled because of #790
https://github.com/rhinstaller/kickstart-tests/blob/master/repo-addrepo-hd-iso.sh

[poncovka]

The plan is to pre-create and use a fake ISO with a repository generated by the generate-repository.py script. The actual content can be always provided by an additional installation source. We already use that trick in some of the kickstart tests.

[rvykydal]

Status update: we haven't seen the flake in our dailies since 10/18/2022 (20 days).

[jkonecny12]

We should probably split ISO generation with the test execution. Like cockpit does. In that case we would be able to gate them "easily".

[poncovka]

We should probably split ISO generation with the test execution. Like cockpit does. In that case we would be able to gate them "easily".

We don't have to gate them at all if there are no real packages on them.

[rvykydal]

Disabling repo-addrepo-hd-tree on rhel10: #1089

[rvykydal]

Disabling on rhel, enabling on Fedora: #1145

[rvykydal]

Marking all the tests with "harddrive" tag in #1210