fix: replace istioctl plugin

[chadlwilson]

Summary

The current plugin (rafik8's plugin) has been broken on MacOS since at least May 2020 due to inconsistency in whether arch suffixes are included (they generally are not, although there is an arm64 build which currently is not supported).

Attempts have been made to get this fixed, but no response, so the plugin appears to not be actively maintained

• URL scheme changed in istio 1.6.0 rafik8/asdf-istioctl#1
• macOS binaries do not have -amd64 or other arch suffix (yet) rafik8/asdf-istioctl#6
• Correct download for osx rafik8/asdf-istioctl#5

By contrast, @virtualstaticvoid 's plugin at https://github.com/virtualstaticvoid/asdf-istioctl is

• working on MacOS
• simple shell script
• has build and tests using the asdf_plugin_test action (here)
• appears to be actively maintained given response on an issue and commits raised in April 2021.

I suggest we switch the default plugin in the registry to this one.

Checklist

• CI tests are green. If you are using GitHub, you might want to use the plugin_test action from asdf-actions
• asdf-plugins CI sanity checks are green on your PullRequest. Test locally with:

./test_plugin.sh --file plugins/<PLUGIN_FILE>

[jthegedus]

Thanks for clearly explaining the history of the current plugin and evidence for it no longer being supported. Saved me a lot of time.

[chadlwilson]

Thanks @jthegedus !