[dmt] Validate package.yaml requirements

[diyliv]

Summary

Add package.yaml requirements validation for the new module requirements schema:

• Parse package.yaml metadata and subscribe sections: Read apiVersion, name, requirements, and subscribe fields used by module package validation.
• Validate package.yaml requirements constraints as-is: Parse all non-empty Kubernetes, Deckhouse, mandatory, conditional, and anyOf module constraints with semver without stripping legacy markers such as !optional.
• Require Deckhouse >= 1.77 for new requirements schema: When the new requirements structure is used, require requirements.deckhouse.constraint and ensure its lower bound starts no lower than 1.77.0.

Example

apiVersion: v2
name: stronghold

requirements:
  kubernetes:
    constraint: ">= 1.26"
  deckhouse:
    constraint: ">= 1.77.0"
  modules:
    mandatory:
      - name: cloud-provider-yandex
        constraint: ">= 1.5.0"
    conditional:
      - name: observability
        constraint: ">= 1.0.0"
    anyOf:
      - description: "One of the following cloud providers must be installed"
        modules:
          - name: cloud-provider-gcp
            constraint: ">= 1.5.0"
          - name: cloud-provider-aws
            constraint: ">= 2.0.0"

Legacy markers in constraint fields are rejected:

requirements:
  modules:
    conditional:
      - name: observability
        constraint: ">= 1.0.0 !optional"