Auto merge of #133247 - GuillaumeGomez:reduce-integer-display-impl, r=workingjubilee

Reduce integer `Display` implementation size

I was thinking about #128204 and how we could reduce the size of the code and just realized that we didn't need the `_fmt` method to be implemented on signed integers, which in turns allow to simplify greatly the macro call.

r? `@workingjubilee`

Author: bors