Add missing arithmetic operations for integer types (Lean)

[clementblaudeau]

In the Lean prelude, some of the (panicking) arithmetic operations are missing, see for instance (addition on u8) :
https://hax-playground.cryspen.com/#lean/latest-main/gist=909e42ba23d6ea1ee254adbd9e7db7b4

The missing operations should be added to the prelude, even without the specification lemmas.