Allow setting the arch of the image to be pulled

[jimmykarily]

because when we are on amd64 host, the auroraboot image is amd64 but we may want to pull and build artifacts for arm64 (e.g. when building rpi raw images). Tested on an amd64 host with this script:

#!/bin/bash

export IMAGE=quay.io/kairos/alpine:3.21-standard-arm64-rpi4-v3.6.0-rc5-k3s-v1.32.9-k3s1

docker run --rm --privileged \
  -v /var/run/docker.sock:/var/run/docker.sock \
  -v $PWD/build/:/output \
  auroraboot:local \
  --debug \
  --set "disable_http_server=true" \
  --set "disable_netboot=true" \
  --set "state_dir=/output" \
  --set "disk.raw=true" \
  --set "arch=arm64" \
  --set "container_image=${IMAGE}"

[Copilot]

Pull Request Overview

This PR enables cross-architecture container image pulling by allowing users to specify the target architecture in the configuration. This is particularly useful when building artifacts for a different architecture than the host system (e.g., building ARM64 images on an AMD64 host).

Key changes:

• Added an Arch field to the configuration schema
• Implemented architecture validation and conversion logic
• Propagated the architecture setting through the image dumping pipeline

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
pkg/schema/config.go	Adds Arch field to configuration schema for specifying container image architecture
pkg/ops/iso.go	Implements WithArch function to validate and set architecture in agent config
pkg/ops/container.go	Updates DumpSource to accept and conditionally apply architecture parameter
deployer/steps.go	Passes architecture from config to DumpSource function

---

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[codecov]

Codecov Report

❌ Patch coverage is 0% with 25 lines in your changes missing coverage. Please review.
✅ Project coverage is 30.54%. Comparing base (02cb529) to head (4f3465a).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/cmd/build-uki.go	0.00%	25 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #388      +/-   ##
==========================================
- Coverage   30.63%   30.54%   -0.09%     
==========================================
  Files          25       25              
  Lines        3023     3045      +22     
==========================================
+ Hits          926      930       +4     
- Misses       1909     1928      +19     
+ Partials      188      187       -1     

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