[rest] have pipelines switch over to rest

[iscai-msft]

fixes #19788

[iscai-msft]

document these as depcrecated, and try to hide with __getattr__ so they don't show up in intellisense

[iscai-msft]

also mention these will be removed in a future release. include in the docstrings

[xiangyan99]

Maybe read_and_close?

[xiangyan99]

great question @xiangyan99

Basically the whole point of this PR is for backcompat reasons. the azure.core.rest and azure.core.pipeline.transport requests and responses have pretty different shapes, and we want the pipelines to fully support azure.core.rest as well. After talking a lot, we decided the cleanest way to support both of these requests and responses was to give azure.core.rest the same shape as the pipeline tranpsort requests and responses (but to give it the same shape secretly, and not document it).

And the reason for having both is that: we kind of only want azure.core.rest, but for backcompat reasons, we have to keep azure.core.pipeline.transport requests and responses. We like the azure.core.rest namespace better as well, it's more user friendly

But this will be very confusing to customers that both of them have same shape but under different namespace.

If I am a customer, how can I know which one to use?

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[iscai-msft]

@xiangyan99 so azure.core.pipeline.transport's requests and responses were what @johanste termed "prevlic", i.e., they're technically public, but we don't expect users to use them. They're not super user friendly and you have to go pretty deep to import them. We also never really publicized users using our requests and responses. When doing LLC, we realized that those old requests and responses were not what we wanted users to use, so we created azure.core.rest.

As to your point about these rquests and responses having the same surface area confusing users over which ones to use,
a. we don't really expect users to have been manually creating and dealing with the old pipeline transport requests and responses, and
b. we're hiding the parts of the surface area that we added to rest to make it compatible with pipeline transport. If you see, we're using __getattr__ and __setattr__ magic so users won't see it documented in sphinx and intellisense