Use std::ops::Range instead of a custom type

[alexcrichton]

This commit removes wasmparser::Range and instead uses
std::ops::Range<usize> instead. This is inspired by review on
bytecodealliance/wasmtime#4005 where it's more convenience to have all
the libstd methods available.

[fitzgen]

What if we just had

pub type Range = std::ops::Range<usize>;

in src/lib.rs?

[fitzgen]

That should cut down churn both in this PR and for downstream crates.

[alexcrichton]

I personally find typedefs like that confusing unless they're well-known which I figure this one probably won't be. I would hope that there wouldn't be too much churn for downstream consumers since this type isn't so common to work with, but are you thinking it'll have a bigger impact?

[fitzgen]

Nah it was just an idea. We can go ahead with this.