Remove ordered_float dependency

[cijothomas]

The SDK currently has a dependency on ordered_float. It is used to provide Hash, PartialEq implementations, for F64 values. While the crate is very popular, it is still a 3rd party dependency, maintained under a personal account.
Proposing to remove the dependency, and make Hash/PartialEq implementation in the opentelemetry crate itself, where Value is defined.

The "correctness" part is not very important - i.e it is undefined if the following would get aggregated into a single metric point or not.

counter.Add(10, &[KeyValue::new("key", F64.Nan)]
counter.Add(10, &[KeyValue::new("key", F64.Nan)]

As a bonus, we can avoid the HashKeyValue wrapper around KeyValue used in Metrics, which solely exist today to provide hash/partialeq implementations.

[cijothomas]

Closed via #1806