Add installer teardown for LUKS and LVM layouts

[kill74]

• This fix issue: Fixes Request: Add teardown function #4491

Fixes #4491

PR Description

This PR adds a guarded teardown path to Installer so archinstall cleans up the target storage stack after an installation attempt exits.

The teardown runs from Installer.__exit__() and is triggered only after mount_ordered_layout() has started. It handles:

• Recursive unmounting of the installation target
• Swap deactivation
• LUKS mapper closure
• LVM logical volume deactivation
• LVM volume group deactivation
• Final udev sync

The cleanup order follows the reverse of the setup topology:

Configuration	Cleanup Order
Plain LUKS	Unmount → close LUKS mappings
Plain LVM	Unmount → deactivate LVM
LVM on LUKS	Unmount → deactivate LVM → close LUKS
LUKS on LVM	Unmount → close LUKS → deactivate LVM

Cleanup is best-effort so teardown does not mask the original installation error.

Tests and Checks

• I have tested the code!

Ran successfully:

python3 -m compileall archinstall/lib/installer.py archinstall/lib/disk/lvm.py

Attempted:

python -m pytest tests

The pytest suite did not complete in the local WSL environment because test collection fails before reaching this change with an unrelated error from archinstall/lib/output.py:

NameError: name 'DataclassInstance' is not defined

That file is outside the scope of this PR.

Manual validation still needed on Arch/live ISO for:

• Plain LUKS
• Plain LVM
• LVM on LUKS
• LUKS on LVM
• No leftover /mnt mounts after installer exit
• No leftover install-created LUKS mappings after installer exit
• LVM volumes/groups deactivated after installer exit