io/ioutil: add deprecation markers to ioutil
All the code in ioutil just forwards functionality to code
in either the io or os packages, per issue 42026.
This change adds the "Deprecated" marker to all the
functions in this package.
For #42026
Fixes #51927
Change-Id: Ia807bc5c0edb06cc80ec7e35917dcfe2ad50f0ea
GitHub-Last-Rev:
3c3603f368e2be517cdd946ae6a666d4e1eda67a
GitHub-Pull-Request: golang/go#51961
Reviewed-on: https://go-review.googlesource.com/c/go/+/395918
Reviewed-by: Emmanuel Odeke <emmanuel@orijtech.com>
Trust: Emmanuel Odeke <emmanuel@orijtech.com>
Run-TryBot: Emmanuel Odeke <emmanuel@orijtech.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>