Process additional Jaeger Span logs

[simitt]

At the moment only error logs are processed and transformed into Elastic APM error events. Record additional Span Logs according to the OpenTracing spec.

Pick up previous discussion about investigating if it makes sense to introduce a dedicated Elastic APM convention for extended support.

[graphaelli]

Linking to #3723. I had thought these would turn into transaction marks originally but generalizing them to actual logs would make them even more useful.

[Dmitry31]

Any future for this feature? There is no clear statement in the documentation about OpenTracing and OpenTelemetry logs support. Looking around on github I feel like Jaeger support is no more a priority as OpenTracing merged into OpenTelemetry ... But OpenTelemetry logs specs are in experimental state so no support neither?

[axw]

@Dmitry31 Jaeger span logs are equivalent to OpenTelemetry span events, so when we get to #4715 we will be able to address this too.