Disable durable scheduler for more OTel calls

[cretz]

What was changed

We already disable durable scheduler for the obvious possibly-non-deterministic OTel calls, but sadly some libraries (like DataDog) monkey patch Context.current which may make illegal calls, and accessing current context is done for most OTel calls.

So this issue disables durable scheduler for more OTel work and adds a test for a monkey patch of Context.current that does illegal things

Checklist

1. Closes [Feature Request] Disable durable scheduler for all OTel in-workflow calls, not just some #359

[chris-olszewski]

LGTM, one small question for my own knowledge

[chris-olszewski]

Is Temporalio::Workflow::Unsafe.durable_scheduler_disabled hefty enough that we want to avoid calling it twice or was the block move just cleaner code?

[cretz]

It's not too bad I don't think, it just unsets the fiber scheduler temporarily and turns off illegal call validation (just a bool setting).

I put in some thought here, but decided I'd rather keep the block-based approach as the only way to disable scheduler currently (instead of also supporting a split disable and re-enable), so I figured splitting the OTel part was better.

(note, my comment refers to "We cannot use ::OpenTelemetry::Trace.with_span here unfortunately", this line of code linked is just code we moved to inside the scheduler disabling)