Fix building with fmt 10.

[FtZPetruska]

Build is failing with fmt 10 due to changes with how enums are treated.

Specifically, an enum now need to have a format_as function, or be casted to its underlying type:

Removed deprecated implicit conversions for enums and conversions to primitive types for compatibility with std::format and to prevent potential ODR violations. Use format_as instead.

[giuspen]

Thanks!