Add support for realm full url retrieval

[davidejensen]

At the moment the client supports a parameter to force the connection to a specific realm.
If in this realm we provide the full url of a realm it works fine, but if we provide the name it fails when trying to perform the request for the /about. (

unity-explorer/Explorer/Assets/Scripts/Global/Dynamic/RealmController.cs

Line 102 in 1ccf8ac

ServerAbout result = await genericGetRequest.OverwriteFromJsonAsync(serverAbout, WRJsonParser.Unity);

)

In order to support the auto retrieval of the full realm url we need to add an integration or a service or an hardcoded mapping of the realm names -> urls.

This issue was spotted as some events on the decentraland website provide the realm parameter that is then passed to the deeplink that opens the app that never loads as it fails on the /about retrieval.

Potentially we could use the apis used by: https://decentraland.github.io/catalyst-monitor/?includeDevServers=