Add private registry configuration to k3k clusters

[galal-hussein]

The PR adds new field to cluster spec:

spec:
....
  privateRegistry:
    secretName: privateregistries
    tlsSecrets:
      ca:
        secretName: ca
      test:
        secretName: test

The controller will read the secret if specified for the privateRegistry and will add registries.yaml file in /opt/rancher/k3s/registry directory, the PR also adds the ability to upload certificates to be used by the registry configuration, each tlsSecrets item is expected to be a TLS type secret that has tls.crt and tls.key field, for each secret the controller will place two files in the directory: /opt/rancher/k3s/registry/ssl, for example with the configuration above, the controller will add the following files to the servers/agents pods:

/opt/rancher/k3s/registry/registries.yaml --> which has the content of registries.yaml item in privateregistries secret
/opt/rancher/k3s/registry/ssl/ca.crt --> which has the content of tls.crt item in ca secret
/opt/rancher/k3s/registry/ssl/ca.key --> which has the content of tls.key item in ca secret
/opt/rancher/k3s/registry/ssl/test.crt --> which has the content of tls.crt item in test secret
/opt/rancher/k3s/registry/ssl/test.key --> which has the content of tls.key item in test secret

• Allow configuration of the registry.yaml of K3s #407

[codecov-commenter]

Codecov Report

❌ Patch coverage is 87.15596% with 14 lines in your changes missing coverage. Please review.
✅ Project coverage is 57.81%. Comparing base (5b4f31e) to head (fbfa0c9).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/apis/k3k.io/v1beta1/zz_generated.deepcopy.go	57.14%	6 Missing ⚠️
pkg/controller/cluster/registry/registry.go	94.20%	2 Missing and 2 partials ⚠️
pkg/controller/cluster/agent/virtual.go	86.66%	1 Missing and 1 partial ⚠️
pkg/controller/cluster/server/server.go	75.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #570      +/-   ##
==========================================
- Coverage   59.54%   57.81%   -1.73%     
==========================================
  Files          56       57       +1     
  Lines        5255     5417     +162     
==========================================
+ Hits         3129     3132       +3     
- Misses       1839     1999     +160     
+ Partials      287      286       -1     

Flag	Coverage Δ
cli	51.73% <3.66%> (-1.73%)	⬇️
controller	55.74% <87.15%> (-1.35%)	⬇️
e2e	55.74% <87.15%> (-1.35%)	⬇️
unit	35.37% <7.33%> (-0.96%)	⬇️

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