As `fileName` makes more sense (as it's not always a lock file we're
updating).
Also, if you set `fileName`, it would never actually output the
filename.
This renames the usages of `lockFile` to `fileName`.
Co-authored-by: Claude Sonnet 4.5 <jamie.tanna+github-copilot@mend.io>
Moves datasource, manager, platform and versioning code from lib/ into new lib/modules/
BREAKING CHANGE: External tools must update paths to datasource, manager, platform and versioning