Remove partial opentelemetry implementation

[ravangen]

Optional followup to #4077 and a comment impacting 2.0.9 and 1.13.13

This PR seeks to return this gem to a "stable state" and not have any misleading or inaccessible code. It is a revert of all the tracing changes with the exception of lib/graphql/tracing/platform_tracing.rb. I still believe there is some value in having a way to access the execution context when tracing, and this was the recommend way to achieve this per #4001.

First-party OpenTelemetry instrumentation would be wonderful, but it was not my intention to force this decision either way as part of the original suggested changes.

Apologies again for the confusion and happy to try and help sort this out based on your recommendations.

[rmosolgo]

Likewise, sorry I misunderstood the nature of these files in the original PR 🤦 I have no preference whether they're here or in opentelemetry-ruby.

My only hangup, IIRC, the only test for passing trace_phase was the opentelemetry tracer itself. If we remove it here, then an over-enthusiastic refactor might remove that option, since it's not used anywhere in this repo.

Would you mind adding a note to the source (or a test, if you can think of a handy way to add one) to help me maintain compatibility in the future?

[rmosolgo]

Added a comment in f4d99f6

[ravangen]

I still will see about adding a test case soon, just to have that peace of mind. Been a bit distracted recently.

[toneymathews]

Can we pls add these changes to 1.13.x as well? I see 1.13.14 still has the opentelemetry implementation.

[rmosolgo]

Oops -- just released this in 1.13.15, too!