otel: automatically inject ContextManager, MetricsProvider, and TraceProvider

[lucacasonato]

Right now you have to import @deno/otel to hook Deno's built in OpenTelemetry API into @opentelemetry/api. @opentelemetry/api however has code to read all three of these from the global object. This code is intended to ensure that multiple copies of @opentelemetry/api can still work correctly.

I propose we set this global on startup as follows:

globalThis[Symbol.for("opentelemetry.js.api.1")] = {
  trace: new Deno.telemetry.TraceProvider(),
  context: new Deno.telemetry.ContextManager(),
  metrics: new Deno.telemetry.MetricsProvider(),
};

This may seem a bit unorthodox, but it is very useful because users do not have to import @deno/otel anymore. This is particularly helpful when using frameworks where you may not control the entrypoint (Next.js, Remix, etc).

I want to run this by the otel-js folks, but I don't think this is really very controversial - one could think of this as bundling @opentelemetry/api and automatically invoking trace.setGlobalTraceProvider and friends on startup.

[lucacasonato]

(This does mean we need to bundle @opentelemetry/sdk-trace-base or a fork thereof to be able to provide a TraceProvider built-in.)