Replace uint by usize in libcore/panicking.rs

[GuillaumeGomez]

Part of #22240.

[rust-highfive]

r? @huonw

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[huonw]

I suspect most of these should be u32: the memory size of the target architecture doesn't relate to the size of the source on the host.

[aturon]

This should be either u32 or u64, you could make an argument for either -- I'd suggest u64 based on the maximum file length we report and the lack of performance issues here.

[GuillaumeGomez]

I was speaking with @aturon about the argument size, I was more for u32 but u64 seems better.

[pnkfelix]

cc #22240

[GuillaumeGomez]

I updated the code. Any thoughts ? @aturon, @huonw ?

[alexcrichton]

I believe this actually ended up getting taken care of in #22853 actually, but thanks for the PR!