Include river errors in server side spans

[cbrewster]

Why

This includes errors on the spans generated by the server so we have more error info.

I also changed the names of the spans to match the format that river-python is using.

In order to write a test for this, I had to make it so the tracer is created per-transport rather than having a global one.

What changed

• De-global the tracer. The transport will construct and own a tracer instance (obtained from the global tracer provider).
• Add river errors to the server side spans
• Update the server/client spans to match the format we are using for river-python
  • This may make it harder to look at historical span data, let me know if you think this is a bad idea and I can revert it

Versioning

• Breaking protocol change
• Breaking ts/js API change

[cbrewster]

Current dependencies on/for this PR:

• main:
  • PR Include river errors in server side spans #283 👈

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