`PartialOrd` requires too many methods in f* core lib

[maximebuyse]

#[derive(PartialEq, Eq)]
struct A(u8);

impl PartialOrd for A {
    fn partial_cmp(&self, other: &A) -> Option<std::cmp::Ordering> {
        (&self.0).partial_cmp(&other.0)
    }
}

Open this code snippet in the playground

This fails because of missing methods. @clementblaudeau this seems to be a regression from 6dede43

[W95Psp]

This is actually because of provided methods: those extra methods are default methods https://doc.rust-lang.org/std/cmp/trait.PartialOrd.html
This is a problem in the F* backend, see issue #888.

So this issue is an instance of #888, but we should probably fix that specific one anyway so let's keep it.

I'll add a comment on your PR otherwise.