Remove usage of baggage in View from initial SDK specification.

[jsuereth]

Fixes #2160

Changes

• Remove the interaction between View configuration + Baggage labels.

This is done to allow room for isntrumentation-library specification and a possible unified Trace/Metric baggage interaction semantic that would be orthogonal to what Views provide.

[cijothomas]

This doesn't prevent a user from manually accessing Baggage, and using values from it as attributes when doing counter.Add(10, {key="foo", value = ""Baggage.GetValue("foo")}), right?

[cijothomas]

Consider adding this to changelog as well.

[jsuereth]

This doesn't prevent a user from manually accessing Baggage, and using values from it as attributes when doing counter.Add(10, {key="foo", value = ""Baggage.GetValue("foo")}), right?

Yes. The idea is that any Baggage => Signal interaction probably should span Traces + Metrics + Logs and we want to save room to figure that aspect out.