Feature: Allow save multi-arch images on `sealos build`

[cnfatal]

What is the problem this feature will solve?

The build-multi-arch-image is designed to build images targeting multi-architecture clusters. However, the images currently loaded into the cluster are single-architecture only. As a result, in mixed-architecture clusters, nodes may pull images that do not match their architecture, leading to unexpected behavior.

If you have solution，please describe it

To address this, I propose introducing a flag such as --multi-arch or --save-multi-arch to allow saving multi-architecture images at build time, it call into sreg and use copy.CopyAllImages to save images.

I’ve done some preliminary work in this area:

• https://github.com/labring/sealos/compare/main...cnfatal:sealos:main

• https://github.com/labring/sreg/compare/main...cnfatal:sreg:main

What alternatives have you considered?

No response

[cuisongliu]

Can you submit PR? Submit the PR of sreg first. @cnfatal