De-duplication of Elastic vs OTel source of data

With OTel -> Elastic bridge implemented for some use cases there will be two sources of spans: for example for PDO there is OTel instrumentation and Elastic legacy instrumentation. We would like to avoid producing two spans for each PDO call instrumented by both OTel and Elastic.

### Implementation notes:
- Possible approach: Mark some spans as leaf (for example PDO and curl) and not create any OTel bridge generated spans under the "leaf" spans