refactor: move from io/ioutil to io and os packages

[Juneezee]

The io/ioutil package has been deprecated in Go 1.16 (See https://golang.org/doc/go1.16#ioutil). Since this project has been upgraded to Go 1.17 in #7029, this PR replaces the existing io/ioutil functions with their new definitions in io and os packages.

Don't bother creating a PR until you've done this:

• Run make pre-commit -B to fix codegen, lint, and commit message problems.

Create your PR as a draft.

• Your PR needs to pass the required checks before it can be approved. If the check is not required (e.g. E2E tests) it
  does not need to pass.
• Once required tests have passed, you can make it "Ready for review".
• Say how how you tested your changes. If you changed the UI, attach screenshots.

Tips:

• If changes were requested, and you've made them, then dismiss the review to get it looked at again.
• Add you organization to USERS.md if you like.
• You can ask for help!

[simster7]

It seems like so from the patch notes, but it's never explicitly mentioned: is the functionality between the ioutil and the io/os functions guaranteed to be the same?

[Juneezee]

It seems like so from the patch notes, but it's never explicitly mentioned: is the functionality between the ioutil and the io/os functions guaranteed to be the same?

@simster7 Hi, thanks for reviewing this PR. Yes, functions in iouti and the io/os functions have the same functionality. These changes should not affect the end users experience as well.

There is one small difference between ioutil.ReadDir and os.ReadDir. The os.ReadDir is proposed (golang/go#41467) for lightweight directory reading, hence it returns []os.DirEntry instead of []os.FileInfo.

[simster7]

This LGTM, but will let @alexec take a look before merging

[alexec]

I'm sorry, I don't think we should accept this PR. The reason is that we often have to back port fixes, and changes to package imports will create a lot of work for anyone doing the back-porting. I don't think that cost outweighs the benefits.