rust http-server: Using u32 rather then usize

[githubsands]

When looking at http-server I believe we could have a more apples to apples comparison by using a u32 or u64 sense the inputs are a positive N. In other cases for signed ints i32 or i64 may be a better comparison.

https://github.com/hanabi1224/Programming-Language-Benchmarks/blob/d454527efb47eb3250f5fc8bb4cb9ac88eb78c67/bench/algorithm/http-server/1.rs#L76

[hanabi1224]

Thanks. I would change all other implementations to use u64, PR is welcome