Migrate goformation under pkg/ as a local package and remove location re-write

[bryantbiggs]

Description

• Migrate goformation under pkg/ as a local package and remove location re-write
  • This removes the second set of dependencies and treats it as a local package, not a remote module

This is to resolve the reported security findings shown here https://github.com/eksctl-io/eksctl/security/dependabot

This is a repeat of #8153 which was reverted since it was caught up in the changes with the failed build image #8157

The steps used to create this PR are as follows (to better understand due to large number of path re-write changes):

1. Move the goformation directory under pkg/
2. Remove the goformation references from the main go.mod file
3. Remove go.mod and go.sum from pkg/goformation/*
4. Re-write paths for goformation (find ./ -type f -name '*.go' -exec sed -i 's|awslabs/goformation/v4|weaveworks/eksctl/pkg/goformation|g' {} \;)
5. Run go mod tidy
6. Run make build
7. Run make unit-test-no-generate to test

Checklist

• Added tests that cover your change (if possible)
• Added/modified documentation as required (such as the README.md, or the userdocs directory)
• Manually tested
• Made sure the title of the PR is a good description that can go into the release notes
• (Core team) Added labels for change area (e.g. area/nodegroup) and kind (e.g. kind/improvement)

BONUS POINTS checklist: complete for good vibes and maybe prizes?! 🤯

• Backfilled missing tests for code in same general area 🎉
• Refactored something and made the world a better place 🌟

[cheeseandcereal]

Thanks, running integration tests on this to see if anything breaks