feat: reduce memory consumption of Scout

[stoo-davies]

Description

Addresses issue 1839, where scout running in VMs uses 10+ GiB of memory.
I've cleaned up the image, and switched to a compressed squashfs based root, rather than decompressing/extracting a cpio image to the ramdisk.

Compatibility with cpio images is retained, as that's being used for some other work, such as the validation image.

Type of Change

• Add - New feature or capability
• Change - Changes in existing functionality
• Fix - Bug fixes
• Remove - Removed features or deprecated functionality
• Internal - Internal changes (refactoring, tests, docs, etc.)

Related Issues (Optional)

#1839

Breaking Changes

• This PR contains breaking changes

Testing

• Unit tests added/updated
• Integration tests added/updated
• Manual testing performed
• No testing required (docs, internal refactor, etc.)

Booted on a x86_64 host, booted/dcgmi run on a H100 and GB200.

Additional Notes

[stoo-davies]

Will set this to draft, I need to fix the "Verify mnv_cli" workflow step to use "unsquashfs -l".

[stoo-davies]

Will set this to draft, I need to fix the "Verify mnv_cli" workflow step to use "unsquashfs -l".

Changes made, mnv_cli test passes now.

[yoks]

Maybe i would try to zero empty space at very end, so image compression would work better, but need to be tested is there any material difference, example could be:

dd if=/dev/zero of=/zero.file bs=1M status=progress || true
rm -f /zero.file

[stoo-davies]

Maybe i would try to zero empty space at very end, so image compression would work better, but need to be tested is there any material difference, example could be:

dd if=/dev/zero of=/zero.file bs=1M status=progress || true
rm -f /zero.file

I'm converting a cpio file to squashfs, no intermediate loop/block filesystem, so that shouldn't be necessary.