[EventHub] Custom exceptions should inherit from azure.core AzureError.

[KieranBrantnerMagee]

Is your feature request related to a problem? Please describe.
Currently, our Exceptions simply derive from Exception.

Describe the solution you'd like
This should be improved to the standard/best practice of inheriting from AzureError at the base.

(not much for further detail as it's a "let's conform to guidelines" issue and somewhat truth-in-advertising per the title.)

[bradleydamato]

Hey @KieranBrantnerMagee ,

I used git grep "(Exception)" to search for custom exceptions that inherit from Exception in azure-sdk-for-python/sdk/eventhub that should be inheriting from AzureError.

I modified the class definitions for those exceptions to inherit from AzureError

Following my changes, git grep yielded no results.

I ran tox tests (see below)

I have a PR here (let me know if I missed anything or misunderstood!): #14432

[KieranBrantnerMagee]

👍 Thanks heartily! Looks like a cogent set of fixes, I'm getting a quick double-check from some of my peers on one of the aspects of it, but your approach was sound and any changes would be us piggybacking on you to make additional improvement :)

[bradleydamato]

Thanks @KieranBrantnerMagee !