Enabled modernize linter configuration.

[atombrella]

Modernize is a golang tool that contains many built-in replacements to use newer golang semantics and standard library features. The PR enables the rules that have been dealt with in the istio repository.

The entire list for GoLang 1.26 is in the documentation.
https://golangci-lint.run/docs/linters/configuration/#modernize

• forvar. I believe it's already covered by copyloopvar, so it's easier to just enable it here.
• rangeint (currently on its way to being enforced in istio in a PR).
• Some strings-rules
• slicescontains and slicessort have only been dealt with in batches. These rules are also quite neat to simplify code.

[istio-policy-bot]

😊 Welcome @atombrella! This is either your first contribution to the Istio tools repo, or it's been
a while since you've been here.

You can learn more about the Istio working groups, Code of Conduct, and contribution guidelines
by referring to Contributing to Istio.

Thanks for contributing!

Courtesy of your friendly welcome wagon.

[istio-testing]

Hi @atombrella. Thanks for your PR.

I'm waiting for a istio member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work.

Tip

We noticed you've done this a few times! Consider joining the org to skip this step and gain /lgtm and other bot rights. We recommend asking approvers on your previous PRs to sponsor you.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Details

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.