Revert "DEPR: is_copy arg of take (#30615)"
This reverts commit 7796be6e2c548de0be16e6adf08f5fca2ab9b4bc.

See https://github.com/pandas-dev/pandas/issues/27357#issuecomment-571639242 and https://github.com/pandas-dev/pandas/pull/30615#issuecomment-571637550
> i would rather fix take later if necessary, rather that redo this PR and fix take later with necessary

If we want to fix `take` later, why should we remove that behaviour of `take` now which we want to preserve later? (the fact that `take` is an actual copy)

BTW, I can also try to do a PR that actually fixes `take`. This is basically https://github.com/pandas-dev/pandas/pull/30784, but in addition we would need to keep a private version of `take` that does the `set_is_copy` thing and ensure to use that private version where appropriate (i.e. mainly in the indexing code). 
But then I first like to have some agreement on that general idea before putting time in it. > > i would rather fix take later if necessary, rather that redo this PR and fix take later with necessary
> 
> If we want to fix `take` later, why should we remove that behaviour of `take` now which we want to preserve later? (the fact that `take` is an actual copy)
> 
> BTW, I can also try to do a PR that actually fixes `take`. This is basically #30784, but in addition we would need to keep a private version of `take` that does the `set_is_copy` thing and ensure to use that private version where appropriate (i.e. mainly in the indexing code).
> But then I first like to have some agreement on that general idea before putting time in it.

that would be preferable

when private and public take were consolidated a while back this must have been broken

also include the tests for no setting with copy warning

thanks @jreback ok, did what is described above in https://github.com/pandas-dev/pandas/pull/30784

So closing this PR then