Centralize logic for template precedence/identity values

[wtgodbe]

dotnet/maui has a property they use for template precedence/identity: https://github.com/dotnet/maui/blob/074554dfd2db8d918a00c014ab3de72ab89398b1/src/Templates/src/templates/maui-blazor/.template.config/template.json#L5-L7. We should do the same so we don't have to manually update every file every year.

[ghost]

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