Infer service name and set it at startup

[jackshirazi]

Is your feature request related to a problem?

If service name is not explicitly set (using the two options) then there is a generic default unknown_service. This is not useful for auto-instrumentation

Describe the solution you'd like

The service name should be inferred as best as possible, if some property is set to true (eg OTEL_ELASTIC_AUTO_SERVICE_NAME=true).

Describe alternatives you've considered

Suggestions welcome

Additional context

While in most cases you can ask the user to set the service name explicitly - which is best practice - in the case of zero-code configuration this would add additional per deployment configuration which is not the optimal experience