Rename RDNN to io.elementary.contractor

[drowsymike]

In discussions elementary/contractor#31 and elementary/contractor#41, @ryonakano pointed out the need to transition from org.elementary.Contractor to io.elementary.Contractor as part of the RDNN rename for OS 9

This PR updates the occurrences in lib/Services/ContractorProxy.vala to match the changes in the Contractor daemon

Note: This change is part of a cross-repo transition and should be merged in coordination with the Contractor PR

[danirabbit]

Since this is an API breaking change we also need to bump the library major version. So this would have to come after we change to granite-9

[ryonakano]

Since now we bumped to granite-9 in the main branch, maybe we can go ahead and merge this?

[ryonakano]

@danirabbit

Since this is an API breaking change we also need to bump the library major version. So this would have to come after we change to granite-9

I'm thinking this back after merging this PR; is this really an API breaking change? As I understand correctly apps that want to use Contractor communicate with it through the APIs in Granite. Here, all of our apps that use Contractor still uses Granite 6 because they have not been ported to GTK 4. So, I wonder possibly we need to rather backport this to Granite 6, otherwise we can never release new version of Contractor with the new RDNN until we port these apps to GTK 4 and Granite 9.