Support batch version metadata retrieval via get-version-metadata --all-versions

[koraytutuncu]

• Adds a new --all-versions workflow to get-version-metadata, letting users fetch every human-readable display version in one run instead of looping through external version IDs manually; the original single-ID path still works unchanged.
• Batch mode records {externalVersionID, displayVersion, success} for each lookup, only attaches error details when --verbose isenabled, and returns a non-zero exit if any version fails so callers can spot partial results.
• Updates the README to document both flag behaviors and note that the bulk mode hits private endpoints per version, suggesting a secondary Apple Account for anyone worried about account safety.