Make winrepo package names work for pkg states

This adds a reverse name map to the repo data that is created by the
winrepo.genrepo runner, and removes some windows-specific code from the
pkg state since we no longer have to work around the fact that winrepo
packages are discovered with their full names.
Remove __context__ from get_repo_data

This is causing a traceback in the pkg state. Will have to figure out
how to fix this.
Merge pull request #5657 from terminalmage/issue5422

Make winrepo package names work for pkg states