[Identity] Change base type of IdentityClientOptions to PipelineOptions

[daviwil]

This change updates IdentityClientOptions to be based on PipelineOptions instead of ServiceClientOptions. The change went very smoothly; the majority of changes were adding expected trace spans for core-http since the tracingPolicy wasn't being added to the pipeline in tests before this commit.

[ramya-rao-a]

@daviwil You mentioned that there is a node vs browser difference you were worried about here. Can you elaborate? Otherwise this change looks good to me

[daviwil]

What I'm seeing is that in the Node.js tests, log messages are only being written when Identity's logger instance is called directly. Any log messages from logPolicy are not written out. In the browser tests, I see logs from both Identity's logger and the logPolicy.

The test code uses setLogLevel to change the log level to verbose before running code to verify log messages were written. @chradek and I observed yesterday that calling setLogLevel After the logger instance was already created actually didn't cause the log level to be propagated to loggers so the expected log messages were not being written out. I think there may be a bug in @azure/logger that we need to investigate; I don't think it has anything to do with this PR.

[ramya-rao-a]

@daviwil In that case, can we log an issue for the logger?

[daviwil]

Yep, I'll file the issue for logger.

[daviwil]

Approved by adpship.