Ensure all examples are working

[dyladan]

All examples should be working before we go to GA. This may require updating some of the examples API 1.x.

[CptSchnitz]

Hi i would like to work on this.
two quick questions:

1. If i find some problems, should i open a PR for each example or one big PR for everything?
2. Is Move examples that depends on contrib repo to contrib repo #1812 also relevant to this?

[Flarna]

I think if a change needed is just a missing import, some minor rename or change of a version it's fine to combine several fixes in one PR. But if there is more to do a dedicated PR is usually better.

[CptSchnitz]

I went over all of the examples, and all of them worked except metrics, Prometheus and opentracing-shim that were missing @opentelemetry/api so it was impossible to run them.
I opened a PR to fix those, and upgrade the @opentelemetry/api version for all of them to the latest.

[dyladan]

Fixed by #2358