Kubernetes Upgrade Investigation and Tests

[Rotfuks]

Motivation

We currently are some major versions behind the most current K8S version (at this point in time v1.24.0 (ours) vs. 1.29.0 (current). We need to investigate what's the best way forward to bridge the gap and test if we can maybe skip multiple versions, just upgrade the CPs or what's the fastest and easiest way to get to the newest version.

### Stories
- [ ] Investigate: can we really skip Kubernetes versions?
- [ ] Investigate options for getting to >1.28
- [ ] Test some assumptions around the options

Outcome

• We have a roadmap ahead on how to get to >1.28 k8s release.

[AverageMarcus]

While I think about it... some things that will need to be done:

• [ ] Re-build all the v1.25->v1.29 VM images using capi-image-builder to ensure they all have the latest patches and include the Teleport changes (and overwrite the ones that currently exist and aren't being used)
• [ ] Run the CNCF conformance tests against each major version for each provider
• [ ] (Maybe) look at testing multiple kubernetes versions using the E2E test suite (could be handled using extra test suites that override the version in the chart values)
• [ ] Upgrade the MCs and handle all the needed mc-bootstrap changes, e.g. with vcluster (we're still only at v1.24 for the MCs)