conflent-kafka: Proxy producer purge

[joshschltelus]

Description

Adds purge to proxy producer

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

from confluent_kafka import Producer
from opentelemetry.instrumentation.confluent_kafka import ConfluentKafkaInstrumentor

instrumentor = ConfluentKafkaInstrumentor()
producer = instrumentor.instrument_producer(Producer({'bootstrap.servers': "localhost:9092"}))
producer.produce('test', value='test'.encode('utf-8'))
producer.purge(blocking=True)

Does This PR Require a Core Repo Change?

• No.

Checklist:

See contributing.md for styleguide, changelog guidelines, and more.

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: joshschltelus (b663b21, e030f1e, c25462a)