Use the new "Main module's version" feature for the ghasum version command

[ericcornelissen]

Summary

Go 1.24 will introduce a new feature to get the main module's version. This would allow replacing the manually defined version used by ghasum version by a value that's defined at build time. The value will also be more useful as it can include data from the VCS (see this description of the feature for more information). This will also simplify the release process as described here.