Review RabbitMQ instrumentation's semantic conventions usage

[mateuszrzeszutek]

RabbitMQ does not seem to implement messaging semantic conventions correctly, e.g. it uses testTopic -> testTopic send instead of testTopic send as span names.

Additional context
#3295 (comment)

[RashmiRam]

The Producer span names are also not complying with semantic conventions.

Producer Span names are getting generated as ["<exchange> -> <routing key> send"] as per this code here. Cardinality of the routing key can be huge based on individual's use cases.

Spec also says that it should be <message.destination> <operation name>. message.destination for RabbitMQ producer span is exchange name only.

Shouldn't this just be "<exchange> send" similar to how Kafka instrument works?

[RashmiRam]

@mateuszrzeszutek If it's alright, Shall I raise a PR to fix this one?

[mateuszrzeszutek]

Sure, that'd be great help!