Improve rke2-uninstall.ps1

[manuelbuil]

Proposed Changes

After a QA iteration, we realized that the previous PR fixing the rke2 uninstallation is still not capable of removing all containerd resources in all environments. Main detected problems:

1 - Time out is too small for certain environments
2 - If we try removing the containerd namespace when there are resources there is an error message which could be confusing for some users
3 - Rarely snapshots get stuck and they require to be removed explicitly

This PR does the following:
1 - Increases the timeout to 3 minutes
2 - To avoid the confusing error message, it does not try to remove the containerd namespace until all the snapshots are gone. Note that the typical resources in a containerd namespace are tasks, containers, images and snapshots. We are removing the first three and once those three are removed, snapshots should be empty (except when snapshots get stuck)
3 - If timeout is reached, we try to remove the snapshots explicitly. If the namespace still can't be removed, we warn the user that the uninstall script might leave some files behind in /var/lib/rancher/rke2
4 - It adds some extra logs and comments to clarify what's going on

Types of Changes

Bugfix

Verification

Install rke2 on linux and windows. Deploy a pod in windows. Run the rke2-uninstall.ps1 script. Without this PR, half of the time the script will fail and it will be impossible to remove the directory /var/lib/rancher.

With this PR, the script works and /var/lib/rancher does not exist anymore

Testing

Linked Issues

#5778

User-Facing Change

Further Comments

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 26.09%. Comparing base (71d00cc) to head (04dff5a).
Report is 155 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6098      +/-   ##
==========================================
- Coverage   26.10%   26.09%   -0.01%     
==========================================
  Files          32       32              
  Lines        2697     2698       +1     
==========================================
  Hits          704      704              
- Misses       1947     1948       +1     
  Partials       46       46              

Flag	Coverage Δ
inttests	9.82% <ø> (-0.01%)	⬇️
unittests	18.57% <ø> (-0.01%)	⬇️

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