refactor(lint): add helm templates validation

[diafour]

Description

• Use kubeconform to validate helm templates with OpenAPI schemas
• Add task to run validation in CI and locally.
• kubeconform will run via Docker if not installed locally.
• Download Deckhouse CRDs from main branch.
• Virtualization module CRDs are used from /crds directory.

Why do we need it, and what problem does it solve?

Helm templates are error-prone, kubeconform helps us to catch various problems.

What is the expected result?

kubeconform report should be in the job output.

Report example:

--- Kubeconform report ---
VALID     APIService v1alpha2.subresources.virtualization.deckhouse.io
VALID     Certificate virtualization
... skip long output with valid resources ...
VALID     VirtualMachineClass host-passthrough
ERROR     Job virtualization-pre-delete-hook
  error unmarshalling resource: error converting YAML to JSON: yaml: unmarshal errors:
    line 21: key "labels" already set in map
ERROR     ServiceMonitor virtualization-virt-handler
  error unmarshalling resource: error converting YAML to JSON: yaml: unmarshal errors:
    line 235: key "namespaceSelector" already set in map
    line 238: key "selector" already set in map
    line 19: key "spec" already set in map
INVALID   Service virtualization-controller-metrics
  - /spec/ports/0:
      additionalProperties 'clusterIP', 'type' not allowed
------- Summary -------
      valid: 97
    skipped: 0
  no schema: 0
     errors: 2
    invalid: 1
task: Failed to run task "validation:helm-templates": exit status 3

Checklist

• The code is covered by unit tests.
• e2e tests passed.
• Documentation updated according to the changes.
• Changes were tested in the Kubernetes cluster manually.