Consider moving the OT shim to Instrumentation

[carlosalberto]

My impression is that most users of OT use it in manual fashion, i.e. no automatic instrumentation. But we should do a double check in case there's value in putting the OT Shim right in the Instrumentation repo.

[jkwatson]

Can I assign this to you, @carlosalberto ?

[jack-berg]

In #4753 we discussed scope of the various repositories and determined that this repo is the correct place for shims defined in the specification like open tracing.