TextResourceRedirector: use mapping registration to support fallback (optional)

[GeBo1]

When the KKS changes promote it will include the ability to map groups of assets that can be searched when the direct asset does not contain a translation. Initial experiments performed poorly so are currently disabled in releases, but it should be possible to refactor using the changes in bbepis/XUnity.AutoTranslator#202 and add some caching of the fallback dictionaries.