Make shared strings public to enable FieldWorks SDK style builds

[jasonleenaylor]

• In the old build system somehow using the same namespace in the FieldWorks code and in this library was enough to get internal access to the strings resources. Update these strings to public so that FieldWorks can use them in its UI.

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This change is 

[Copilot]

Pull Request Overview

This PR makes shared string resources public to enable FieldWorks SDK style builds. The change addresses a compatibility issue where the old build system allowed internal access to string resources through namespace sharing, but this no longer works in the new build system.

Key Changes

• Updated the ResX code generator to produce public string resources instead of internal ones

Files not reviewed (1)

• src/SIL.LCModel.FixData/Strings.Designer.cs: Language not supported

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