Implement `ISpanFormattable` and `ISpanParsable` in source-generated IDs

[jakubfijalkowski]

          Can we also add and implement `ISpanFormattable` and `ISpanParsable`? They are very useful when performing string interpolation/formatting (and they would be even more useful if we used any stringlike type (Ulid? :stuck_out_tongue:) that isn't directly supported by STJ).

Originally posted by @Saancreed in #466 (comment)