Replace the usage of go-homedir with os.UserHomeDir()

[folliehiyuki]

go-homedir project has been archived for a long time. os.UserHomeDir() returns the same value set so we can use it as a drop-in replacement. Sadly, some vendored modules still depend on go-homedir. The offended modules are github.com/awslabs/amazon-ecr-credential-helper and github.com/Azure/go-autorest, which are both pulled by the direct dependency github.com/google/go-containerregistry/pkg/authn/k8schain.

Ref: mitchellh/go-homedir#34

[pascalbreuninger]

@folliehiyuki thanks for the contribution!
I understand that it's simpler to use os.UserHomeDir() instead of go-homedir but go-homedir has a couple of nice fallbacks like reading /etc/passwd if the user env var isn't specified. I don't exactly know if it will break if we change it but I'd also rather not take our chances here.

Since go-homedir is archived and small enough it might be just fine to put it's code somewhere under /pkg, wyt?

[folliehiyuki]

Sounds okay to me. I've copied the code from go-homedir with some modifications into pkg/util. If you prefer somewhere else I'll update it.

The only difference I see between go-homedir and os.UserHomeDir() is that the former always checks for $HOME even on Windows, so I added a test case for it. I don't use Windows so haven't actually verified the test.

[pascalbreuninger]

Sounds good, thank you!

[pascalbreuninger]

LGTM 🙌

[pascalbreuninger]

The linting CI failed and I've fixed it quickly. Hope you don't mind @folliehiyuki