[azservicebus] Document best practices and considerations for the library

[richardpark-msft]

This came up in #22629, where the original question (do you support retries) went into an interesting discussion when we looked at how they got there. The big piece that I think we're missing is some general discussion about what areas can be tuned, and how they work.

Some things I can think of:

• Being aware of connection sharing
• Being aware of which aspects of the SDK are safe to use in a multithreaded way (ie, all of it, but people might not think about it being beneficial)
• Batching messages vs sending single messages
• Tuning ReceiveMessages() calls - max wait time + max batch wait time
• Retry policy tuning (our policy is very conservative)

[github-actions]

Thanks for the feedback! We are routing this to the appropriate team for follow-up. cc @EldertGrootenboer @jfggdl.

[richardpark-msft]

(@EldertGrootenboer , @jfggdl ) incorrect routing, no service attention required for this one.