Baggage <-> Context interaction on Baggage as static methods?

[jsuereth]

The Specificaiton states that baggage should have convenience methods to go to/from context.

Currently, that resides in the propagation module of Bagage,

However, given that interacting with baggage is not just a component of propagation and how most SDKs provide To/From context methods directly on baggage (or at least in the same package/header), I suggest Baggage should have static to/from context methods (or a header file within the baggage directory that provide this functionality.

Effectively, let's not conflate using Baggage with propagation of baggage.