Use B3-Propagation for Tracing Headers
The Tracing headers which we use now X-Hasura- are not
standard,though they help us trace requests within our
systems but this willbreak/not work when we tend to use
the other Trace Recorders.Hence it's better to refactor
the code to allow using at least B3 headers for now.
i#Refractor injectHTTPContext
Co-authored-by: Phil Freeman <phil@hasura.io>