MUX Experimental: ResourceAccessor::GetLocalizedStringResourceFromWinUI has hardcoded string for WinUI 2.6

[kmahone]

In the MUX Experimental dll, ResourceAccessor::GetLocalizedStringResourceFromWinUI is used to lookup localized resources from the regular WinUI package.

This initially used the MUXCONTROLS_PACKAGE_NAME macro to get string. But after merging the latest from main branch, this no longer works, since main is on 2.8, but Experimental is tied to 2.6.

We need to rationalize how versioning works with Experimental depending on the main WinUI package