Rename AutoCleanup to CleanupPrereleases for clearer naming

[MariusStorhaug]

Summary

The current setting AutoCleanup should be renamed to CleanupPrereleases to better reflect what it actually does - cleaning up prerelease tags after a stable release is created.

Context

This rename was initially attempted as part of the ReleaseType feature work, but was reverted to avoid an unnecessary breaking change in that PR. This issue tracks the rename as a separate, focused change.

Changes Required

The rename needs to be coordinated across:

• Get-PSModuleSettings: Update Publish.Module.AutoCleanup to Publish.Module.CleanupPrereleases
• Publish-PSModule: Update AutoCleanup input to CleanupPrereleases
• Process-PSModule: Update workflow to use the new input name

Notes

• This is a breaking change for users who have explicitly set AutoCleanup in their PSModule.yml
• Consider adding backwards compatibility by accepting both names during a transition period