The copy in the packages table (too many results to show, etc...) was
not centered because the table actually has 5 columns, not 4. This fixes
the problem.
Previously we've used two steps for adding packages - the Additional Red Hat packages and Additional Custom packages steps. This merges the two steps into one.
Also the steps originally used `DualListSelector` to show the packages options, this was now migrated to the packages `Table` which makes the step visually consistent with the Repositories one. Although the functionality is a bit different.
Repositories step fetches the complete list of repositories right at the beginning and then mutates it by filtering. The Packages step fetches the data based on a search term which means that the "All" table gets overwritten by new values anytime a new term is searched.
Previously used axios API calls were also migrated to RTK Query for the purpose of consistency.
