Refactoring the provider to unit test create cluster

[Skarlso]

Description

Ground work for #5015.

What happens in this PR?

1. Renamed Provider to AWSProvider since it provides AWS functionality
2. ClusterProvider is no longer a KubeProvider. It has been extracted into a separate part so it can be mocked more easily
3. doClusterCreate now gets the ctl passed in from the outside so we can mock it
4. Several small refactors and test changes for mock calls

Integration test run https://github.com/weaveworks/eksctl-ci/actions/runs/2330469236

edit: New test run https://github.com/weaveworks/eksctl-ci/actions/runs/2332032290

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 🌟

[Skarlso]

Integration tests passed except for a single test which timed out on TLS. That appears to be a fluke from AWS though. I'm running it locally to verify that.

Edit: Works:

Ran 3 of 3 Specs in 156.705 seconds
SUCCESS! -- 3 Passed | 0 Failed | 0 Pending | 0 Skipped
--- PASS: TestBeforeActive (156.71s)
PASS

[cPu1]

Just one comment about considering embedding KubeProvider, but otherwise LGTM.

My deadline-based Context PR will result in conflicts, so I'll wait for this to be merged before merging mine.

[Himangini]

LGTM 👍🏻