Add presubmit check to prevent accidental go directive bump

[sbueringer]

In Cluster API we only bump the go directive in go.mod files on the main branch.

While we bump the Go minor version that we build release branches with we never bump the go directive there.

This issue is about adding a presubmit check to ensure we don't accidentally bump it.

This can be implemented by adding a new verify-go-directive Makefile target (prior art: https://github.com/kubernetes/utils/pull/306/files) and then adding it to the verify target we already run in CI.

For more context, see: kubernetes/kubernetes#123744

[sbueringer]

/triage accepted
/help wanted

[MadhavJivrajani]

/help

[k8s-ci-robot]

@MadhavJivrajani:
This request has been marked as needing help from a contributor.

Guidelines

Please ensure that the issue body includes answers to the following questions:

• Why are we solving this issue?
• To address this issue, are there any code changes? If there are code changes, what needs to be done in the code and what places can the assignee treat as reference points?
• Does this issue have zero to low barrier of entry?
• How can the assignee reach out to you for help?

For more details on the requirements of such an issue, please see here and ensure that they are met.

If this request no longer meets these requirements, the label can be removed
by commenting with the /remove-help command.

In response to this:

/help

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/test-infra repository.

[AvineshTripathi]

/assign