[feat] templates: add Flatcar template

[tormath1]

It is based on vpcless.

What this PR does / why we need it: This PR brings Flatcar templates to CAPL

Special notes for your reviewer:

• For now it is based on vpcless - using kubeadm default template makes the metadata server returning 500 Internal error
• Because the user-data is limited in size, I can't setup the Kubernetes sysext auto-update on Kubernetes patch releases

 $ kubectl --kubeconfig=./${CLUSTER_NAME}.kubeconfig get nodes -w
NAME                               STATUS   ROLES           AGE     VERSION
test-cluster-control-plane-fb9xm   Ready    control-plane   6m22s   v1.29.5
test-cluster-md-0-ccq4p-gdcn9      Ready    <none>          2m16s   v1.29.5
test-cluster-md-0-ccq4p-lsjtj      Ready    <none>          3m17s   v1.29.5
test-cluster-md-0-ccq4p-lxpwp      Ready    <none>          2m14s   v1.29.5
$ make e2etest E2E_SELECTOR='flatcar' E2E_FLAGS='--assert-timeout 10m0s'
...
--- PASS: chainsaw (0.00s)
    --- PASS: chainsaw/flatcar-capl-cluster (463.58s)
PASS
Tests Summary...
- Passed  tests 1
- Failed  tests 0
- Skipped tests 0
Done.

TODOs:

• squashed commits
• includes documentation
• adds unit tests
• adds or updates e2e tests

[codecov]

Codecov Report

Attention: Patch coverage is 25.00000% with 12 lines in your changes missing coverage. Please review.

Project coverage is 64.65%. Comparing base (e83dc0c) to head (641aba9).

Files	Patch %	Lines
controller/linodemachine_controller.go	25.00%	9 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #394      +/-   ##
==========================================
- Coverage   64.80%   64.65%   -0.15%     
==========================================
  Files          68       68              
  Lines        3506     3517      +11     
==========================================
+ Hits         2272     2274       +2     
- Misses       1054     1061       +7     
- Partials      180      182       +2     

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[tormath1]

ready for final review

[tormath1]

rebased on main and moved the Configuration changes from v1alpha1 to to v1alpha2