Refactor: Improve Boot Exclusion in diskutils.go for EMT ISO Installer

[Jkintalix]

• Refactored SystemBlockDevices to build the device list incrementally instead of pre-allocating with fixed size.
• Integrated isReadOnlyISO checks to exclude ISO installer devices.

Merge Checklist

All boxes should be checked before merging the PR

• The changes in the PR have been built and tested
• [] cgmanifest file has been updated if required
• Ready to merge

Description

For reference to ITEP-70891: This change refactors SystemBlockDevices to exclude boot and ISO devices from the returned list of installation targets. Previously, all block devices were included, which risked accidentally selecting the root disk or mounted ISO images during installation. The update introduces new helper functions: isReadOnlyISO to filter devices mounted as read-only. With these improvements, the EMT ISO installer now only considers safe, valid disks for installation, reducing the risk of overwriting the boot disk or ISO media

The EMT ISO installer was incorrectly listing the system’s boot device and mounted ISO devices as valid installation targets. This created a risk of overwriting the active root disk or the installation media itself, leading to failed or unstable installations. The filtering logic for excluding boot/ISO devices already exists in the graphical installer, and this update brings the same robustness to the EMT ISO installer.

Any Newly Introduced Dependencies

No

How Has This Been Tested?

Tested ISO locally.

Terminal disk selection page:

[yepmunchun]

If we just need to exclude the device that currently acting as the installer, isn't that the isBootDevice check is sufficient? Why do we still need isISODevice and isReadOnlyISO check?

[Jkintalix]

If we just need to exclude the device that currently acting as the installer, isn't that the isBootDevice check is sufficient? Why do we still need isISODevice and isReadOnlyISO check?

Thanks for the review! isBootDevice catches the active installer device via /proc/cmdline and /proc/mounts, but isISODevice and isReadOnlyISO are needed to exclude non-boot ISO9660 devices (e.g., a secondary USB) that could be installer media. isISODevice flags ISO filesystems with blkid, and isReadOnlyISO confirms read-only status to avoid writable disks. This ensures safety in multi-device setups

[yepmunchun]

I think the original issue is to prevent the currently active installer from being selected as the installation target.
If there are other devices containing ISO installer/ISO installed image, those devices should remain available for selection as an installation target.

[Jkintalix]

I think the original issue is to prevent the currently active installer from being selected as the installation target. If there are other devices containing ISO installer/ISO installed image, those devices should remain available for selection as an installation target.

Addressed