[PoC] Automated regression testing of manual XCP-ng installation - #643

The automated installation tests rely on creating an answerfile with the proper configuration, and remastering the chosen install ISO in order to use that answerfile by default. This is convenient to create all kinds of different configuration, but it does not test the manuel install process since the TUI is completely avoided.

This proof of concept shows that a manual installation can also be automated in order to test for potential regression in the TUI. More specifically, this PR introduces a couple of tests, following the dependency convention introduced in tests/install/test.py:

± uv run pytest --hosts 10.1.0.11 tests/install/with_tui.py --co -q
tests/install/with_tui.py::test_install_with_tui[uefi-83nightly-iso-ext]
tests/install/with_tui.py::test_tune_firstboot[None-uefi-83nightly-host1-iso-ext]
tests/install/with_tui.py::test_tune_firstboot[None-uefi-83nightly-host2-iso-ext]
tests/install/with_tui.py::test_boot_inst[uefi-83nightly-host1-iso-ext]
tests/install/with_tui.py::test_boot_inst[uefi-83nightly-host2-iso-ext]

The interesting part is the test_install_with_tui test. Here's what it does:

• It creates a new VM in an L0 pool, using a configuration similar to what happens in tests/isntall/test.py. One notable difference is that it sets platform:hvm_serial to pty
• It uploads the selected nightly ISO to the ISO SR of the L0 pool (it also caches the ISO, although this part was mainly introduced to speedup the development process). Note that it does not require any remastering.
• It inserts the install ISO and start the VM. Then it connects to the serial line by ssh-ing to the resident host and using xl console -t serial $domain_id
• Note that paramiko is used to allocate a pty. This allows proper control of the interactive sessions. The test logs the installation message, and then navigate through the dialogs, mostly using the default options.
• It then install XCP-ng, and shutdown once the installation is completed. The nested host is then cached for the upcoming test_tune_firstboot test.

Note that the nested hosts produced by test_boot_inst can run the postinstall test job:

uv run jobs.py run postinstall "cache://install.with_tui::boot_inst[uefi-83nightly-host1-iso-ext]-vm1-c6b8d6ef415549749ed22d0b155a9dc200c55824" --nest 10.1.0.11