Used by appenders and processors for mapping from bridges to OTel and nothing else (does not go over the wire).

Prototypes needed for stabilization:

• Log4j - Implement otel.event.name opentelemetry-java-instrumentation#16220
• Logback - Implement otel.event.name opentelemetry-java-instrumentation#16220
• Go (log processor) - https://pkg.go.dev/go.opentelemetry.io/otel/sdk/log#example-Processor-EventName

Behavior:

• bridge sets it as EventName top-level and does not set the attribute
• OR a log processor sets the top-level EventName

This allows to decouple new thing vs event.name which has different meaning (goes over the wire, has prior instrumentations and behavior).

We should also re-deprecate event.name.
EDIT (pellared): Done in #2914