What does this PR do?

We had previous PRs at #5335 and elastic/beats#42025 moving away from math/rand to the newer math/rand/v2 package. Currently there is nothing preventing contributors to commiting code using math/rand and regressing these changes.

Introduce a linter that catches math/rand imports in Go files.

Checklist

• I have read and understood the pull request guidelines of this project.
• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in ./changelog/fragments using the changelog tool
• I have added an integration test or an E2E test

Related issues

• Use math/rand/v2 in place of math/rand #5335