Add Span's IsRecordingEvents

[carlosalberto]

https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/api-tracing.md#isrecordingevents

[mauriciovasquezbernal]

I think this is solved by #141.

[Oberon00]

Indeed:

opentelemetry-python/opentelemetry-api/src/opentelemetry/trace/__init__.py

Line 222 in 83aad2f

def is_recording_events(self) -> bool: