fix(tag-from-scope), merge package.json props from the last snap

[davidfirst]

The need came from Angular components. Angular env uses ng-packgr to compile components during build, this tool modifies the package.json and adds different values into exports prop. Because the modification is done during build pipeline and is not saved as an artifact, it gets lost when tagging from scope.
As a reminder, tag-from-scope copies artifacts from the last snap into the capsule and only runs the tag-pipeline.
This PR, uses the package.json saved in the last snap and merge its properties into the current package.json of the capsule. It can't simply replace it, because some values, such as version and dependencies versions are changed in this tag.