Honor IO errors in list-images sub-command

[twz123]

Description

Previously, the sub-command did not interrupt the loop and returned successfully, even when it encountered IO errors while writing to standard out.

Use strings.Builder instead of bytes.Buffer: The out and err streams are always treated as strings for better readability, so it's more idiomatic to use strings.Builder for them. Replace intoLines with strings.Split, as strings.Builder doesn't implement io.Reader, which eliminates another helper function on the fly.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

How Has This Been Tested?

• Manual test
• Auto test added

Checklist:

• My code follows the style guidelines of this project
• My commit messages are signed-off
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings