MSI: Cleanup and improved error handling

[lrandersson]

Description

This PR contains a small set of generic improvements that I wanted to make to account for all the recent updates. This removes some redundancy and contains improved error handling.

1. create() function improvements:

• Changed generic Exception to OSError for platform check (OS-level constraint)
• Changed generic Exception to ValueError for missing logging support (invalid configuration)
• Moved briefcase existence check before payload.prepare() to fail fast
• Added try/finally to ensure payload.remove() cleanup runs even on failure

2. Payload.prepare() cleanup:

• Removed unused return value (root, external_dir, base_dir, pkgs_dir) - it didn't make any sense to return paths that don't exist (due to the archiving)

Checklist - did you ...

• Add a file to the news directory (using the template) for the next release's release notes?
• Add / update necessary tests?
• Add / update outdated documentation?