[core-auth] shouldn't export OperationOptions

[xirzec]

In #5899 we ended up exporting an interface called "OperationOptions" that isn't exactly the same as the one in core-http, but structurally compatible.

This can create a big of confusion, so for now we should stop exporting this interface and inline all necessary options to GetTokenOptions until we can put the real OperationOptions in a common place.

/cc @daviwil @bterlson @ramya-rao-a

[ramya-rao-a]

As library authors when we use OperationOptions, auto-complete now gives suggestions from both core-auth and core-http, so we may end up with a mix and match of these.

I agree with @xirzec that we should inline these in core-auth and have a single source of truth for exported interfaces

[daviwil]

Thanks @ramya-rao-a for reminding me to respond to this. Yes, it was a mistake to add another OperationOptions to core-auth, I'm totally on board with removing it and inlining the necessary fields. We'd have to bump the major version of core-auth, but since users shouldn't be depending on this directly it hopefully won't be a problem.

[bterlson]

I think the odds of someone depending on this type by name are so low that we can just consider this a bug fix.