Move OTel code out of integrations/

[sentrivana]

Right now, POTel is written as an integration. This is problematic since it can be disabled via default_integrations=False. Also in architectural sense it's no longer an integration but an integral part of the SDK, so it's time for it to move out of the integrations/ directory.

This should also enable us to clean up the code and get rid of some inline imports due to circular imports.

• Move scope context init outside integration #3850
• remove integrations/opentelemetry/* and move the code where it makes sense